Intel Modem 537EX User Manual

537EX Chipset  
Developer’s Manual  
January 2002  
Order Number: 273584-002  
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Contents  
Contents  
1.1.1 Windows* Millennium Edition (Windows Me), Windows 2000, Windows XP, and  
3.4  
Modem Identification Commands [In, +FMI, +FMR, +FMM, +GMI, +GMM, +GMR, +GSN,  
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Figures  
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Tables  
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Contents  
Revision History  
Date  
Revision  
Description  
Changed references to HaM Data Fax Voiceto Intel 536EP  
V.92 Modem.”  
January 2002  
August 2001  
002  
001  
Initial release  
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Introduction  
1
This developer’s manual describes the software interface for Intel® 536EX (controllerless and  
controller) chipset solutions. The controllerless-based solutions include the 536EP for PCI and  
Mini-PCI. Refer to the chipset datasheets for the detailed chipset descriptions (public order  
numbers 273503-001, 273xxx-001, 273xxx-001, 273xxx-001, and 273xxx-001).  
The controllerless-based chipset, as the name implies, does not have a dedicated hardware  
controller. The controller functions are executed by the CPU. This developer’s manual includes the  
AT command sets for data, fax, and voice and the UART interface and emulation. Like the earlier  
solutions from Intel, the 536EX chipsets support a variety of applications without the need of  
additional firmware development. Note, the supported AT commands are firmware or driver  
version dependent.  
1.1  
Controllerless Modem Driver Overview  
1.1.1  
Windows* Millennium Edition (Windows Me), Windows  
2000, Windows XP, and Windows NT* 4  
The controllerless modem chipsets are integrated into the Microsoft* Windows* Me, Windows  
2000, Windows XP, and Windows NT* 4 operating systems via proprietary Intel® Windows  
Driver Model (WDM) modem drivers. These drivers are fully plug and play capable and conform  
to all Microsoft WHQL certification requirements.  
The functional block diagram in Figure 1 shows the common WDM architecture for the  
Microsoft’s operating systems supporting common WDM drivers model.  
User-mode application, via special Windows API (FILE, TAPI, UNIMODEM), can access a virtual  
COM port provided by the Intel WDM driver. The data flow is converted inside the driver in  
accordance with some compression and a channel level protocol and passed to the DSP. The  
control flow follows the common Microsoft WDM driver model. The Intel WDM driver is  
installed as a stack of filter drivers below the system modem.sys driver.  
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Introduction  
Figure 1. WDM Driver Block Diagram  
User  
applications  
User applications  
Kernel - ring0  
Modem drivers stack  
virtual COM  
port,  
channel  
protocols  
layer  
WDM driver  
Intels51.sys  
PCI bus  
Hardware  
1.1.2  
Windows 95 and Windows 98  
When the controllerless modem chipsets are used with Microsoft Windows 95 and Windows 98  
applications, the traditional UART and serial port emulations are replaced by the proprietary HaM  
Mini Port driver (see Figure 2). Instead of transferring commands to UART virtual registers, then  
to a serial port, the HaM Port Driver sends commands directly to the Windows virtual machine  
driver VCOMM.VxD. This low-level communication driver supports the Win16 and Win32  
Communication APIs. Like the WDM drivers, the Mini Port VxD drivers are fully plug and play  
and conform to Microsoft WHQL certification requirements.  
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Introduction  
When the controllerless chipsets are used with MS-DOS* applications, however, a UART  
emulation is required. Intel provides an additional driver called Intelsdb.VxD, which includes a  
page 92 for an explanation of the 536EX UART emulation. The Intelsdb.VxD driver interacts  
directly with the VCOMM.VxD driver using the Win16 and Win32 Communication APIs.  
Figure 2. VxD Mini Port Driver Block Diagram  
NON-SYSTEM  
VIRTUAL MACHINE  
MS-DOS SHELL APPLICATION  
OR DRIVER  
SYSTEM VIRTUAL MACHINE  
MS-DOS  
APPLICATION  
WINDOWS  
APPLICATION  
Win 16  
TAPI  
Unimodem  
COMM.DRV  
VCOMM.VXD  
Intelsdb.VXD  
HaM Port Driver  
Interrupt Services  
Chipset Hardware  
1.2  
V.90/V.92 and V.34 Data Modes  
The 536EX chipset defaults to the V.90 or V.92 mode depending on the driver version. The V.90/  
V.92 mode allows receive data rates of up to 56,000 kbps over the PSTN (public switched  
telephone network) only in connections with equipment-compatible ISPs (Internet Service  
Providers); however, FCC regulations limit receive speeds to 53,333 kbps due to excessive power  
demands at higher speeds. In modem-to-modem connections, V.90/V.92 mode falls back to V.34  
mode in both the transmit and receive directions. The chipsets implement all data rates and  
modulation schemes for ITU-T (International Telecommunications Union-Telecommunications)  
standards V.34, V.32 bis, V.32, V.22 bis, V.22, V.21, Bell 212A, and Bell 103.  
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Introduction  
1.3  
Modem Connection Overview  
The DCE (modem) operates in one of two states: command or online. In each state, both data and  
commands (including DCE responses) are transferred through the UART THR (Transmit Holding  
register) and the RBR (Receiver Buffer register).  
The modem defaults to the command state. In the command state, the DTE (host) communicates to  
the modem through AT commands and S-registers. AT commands are character strings that help  
guide modem operation. S-registers are internal modem registers that the DTE can access. The S-  
registers contain modem status and configuration information. Many of the AT commands  
indirectly affect the contents of the S-registers. The AT command set and S-registers are divided  
into the following modes: Group 3 fax, data, V.44/V.42 bis/V.42/MNP, and voice. Note that  
supported AT commands are firmware revision-dependent (that is, not all commands are supported  
by all modem models or all firmware revisions).  
All command lines sent to the modem, except for A/, must be preceded by an AT(which stands  
for attention) and terminated by the contents of S-register S3 (typically a carriage return <CR>).  
The ATprompts the modem to receive a command line from the DTE. A <CR> informs the  
modem that the entire command string has been transmitted and that the modem should start  
processing all the commands within the command line.  
A command line may include one or more AT commands that may or may not be separated by a  
space. AT commands may be either upper- or lower-case characters, but all characters for a given  
command must use the same case. If there are multiple commands in a line, a semicolon (;) must be  
placed after each fax or voice command. The modem can be configured to send back (echo) to the  
DTE any data that the DTE sends to the modem (while in command state only). The last command  
may be repeated by typing A/ without using a carriage return. Each command line may include up  
to 80 characters and spaces.  
Examples of AT command strings:  
ATS1?<CR>  
A/  
AT &C1 &D2 +FCLASS=? <CR>  
AT &C1 &D2 +FCLASS=?; S0=1 <CR>  
The modem provides status information to the DTE in the form of response codes. These response  
codes can be expressed in text or numeric form. The supported response codes are provided in  
Examples of modem responses:  
+MCR: V90  
+MRR: 28800  
CONNECT 50666  
In the online state, the DCE is off-hook and communicating with a remote modem. Any data sent  
from the DTE to the DCE is transmitted to the remote modem. Similarly, any data that the DCE  
receives from the remote modem is transmitted to the DTE.  
Note: In the online state, the DCE does not echo-backany of the data that the DTE sent to the DCE.  
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Introduction  
The modem recognizes AT commands from the DTE at any valid data rate from 300 bps to 115,200  
bps (that is, the modem autobauds up to 115,200 bps); however, the DTE should use the data rate  
specified for each mode according to the transmitting directionDTE-to-modem (Table 1) or  
modem-to-modem (Table 2). The V.90 and V.92 data rates are effective only in DCE-to-ISP  
connections.  
Table 1. DTE-to-DCE Data Rates for Each Mode  
Mode  
Data Rate (bps)  
2400115,200  
Affected Data  
Data (V.34)  
Data (V.90)  
Data (V.92)  
Fax  
28,800115,200  
28,800115,200  
19,200  
DTE-to-modem data rate  
AT commands, playback and record modes  
(varies according to compression type)  
Voice  
19,200115,200  
Table 2. DCE-to-DCE Data Rates for Each Mode  
Mode  
Data Rate (bps)  
240033,600  
Affected Data  
Data (V.34)  
(transmit and receive)  
Fax  
DTE-to-modem data rate  
30014,400  
AT commands, playback and record modes  
(varies according to compression type)  
Voice  
19,200115,200  
Table 3. DCE-to-ISP Data Rates for V.90 Mode  
Mode  
Data Rate (bps)  
Affected Data  
Data (V.90) transmit  
Data (V.90) receive  
Data (V.92) transmit  
Data (V.92) receive  
480033,600  
28,00056,000  
24,00048,000  
28,00056,000  
ISP-to-modem data rate  
Each command may have one or more parameters associated with it. If a parameter is not sent for a  
command requiring a numeric parameter, then the modem assumes a zero (0) parameter (only if  
zero is a valid parameter for the command). For example, ATZ and ATZ0 commands perform  
identical functions (that is, the modem sees ATZand automatically uses the 0parameter during  
processing the command). Other commands do not use parameters.  
1.4  
AT Commands Overview  
The AT command set and S-registers are divided into four categories: data, Group 3 fax, voice, and  
V.42/MNP. Summaries of all commands are provided later on in this chapter.  
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Introduction  
1.4.1  
Sending Commands  
All command lines sent to the modem, except for A/, must be preceded by an ATand terminated  
by the contents of S-register S3 (typically a carriage return <CR>). AT stands for attentionand  
prompts the modem to receive a command line from the DTE. A <CR> informs the modem that the  
entire command string has been transmitted and to begin processing all the commands in the  
command line. A command line can include one or more AT commands. The commands can be  
separated by a space, if desired, but no punctuation is needed except for extended commands.  
Extended commands begin with a +, such as fax, voice, and V.250 commands. In a multiple-  
command line, extended AT commands must be separated from following commands by a  
semicolon(;).  
Examples:  
ATS1?<CR>  
A/  
AT &F &D2 +FCLASS=?<CR>  
AT +FCLASS=0; S0=1<CR>  
The modem provides status information to the DTE in the form of response codes, as listed in  
Table 4. Response codes take two (2) forms, text (ATV1) or numeric (ATV0), depending on how  
the modem is configured.  
Table 4 lists basic format response codes. These response codes have numeric equivalents that are  
displayed depending on the value of ATV. In addition to the basic format response codes, there are  
extended syntax result codes that indicate connection status of the DCE-DCE connection that are  
not effected by numeric response reporting. These result codes have no numeric equivalent and are  
always issued in text form. The result codes display modem mode, transmit connection rate, error  
correction, compression, DTE rate, and receive rate. Note that the final connection message only  
indicates receive rate if ATXn is greater than 0. The format for the result codes code depends on the  
Wn command. The setting of the Wn command will determine which of the following connect  
results codes are displayed (+MCR, +MRR, +ER, +DR, +ILRR). Refer to the Wn command for the  
detailed description of the command. Note that the supported carrier modes for +MCR can be  
found in parameter 1 of +MS. The last result code is the CONNECT <text>, where text is the DCE  
receive rate. Note, the CONNECT <text> is not displayed when ATX0 is indicated, just  
CONNECT is displayed and is reported by the rules in Table 4.  
Table 4. DTE-Modem Data Rate Response Codes  
Numeric  
Text  
Numeric  
Text  
0
1
2
3
4
6
7
8
OK  
9
DELAYED CALL  
BLACKLISTED  
+FCERROR  
RINGBACK  
CPON=  
CONNECT  
RING  
10  
11  
12  
13  
14  
15  
16  
NO CARRIER  
ERROR  
NO DIALTONE  
BUSY  
CPOF=  
DRON=  
NO ANSWER  
DROF=  
After sending an AT command string to the modem, the DTE must wait for a response code from  
the modem before sending a new AT command string to the modem.  
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Introduction  
1.4.2  
AT Escape Sequences  
The 536EX provides the industry-standard escape sequence, TIES (Time Independent Escape  
Sequence). TIES is designed to work with existing communication software written for the Hayes  
Escape Sequence.  
Upon special request, Ambient provides the Hayes* Escape Sequence; however, please note that  
licensing can be required.  
TIES/Hayes* Escape Sequences  
The 536EX modem chipset is manufactured with TIES (Time Independent Escape Sequence) as  
the default setting. It is Hayesposition that you must have a valid license from Hayes Micro  
Computer of Norcross, Georgia, before producing modem systems that use the Hayes Escape  
Sequence.  
Intel accepts no responsibility and does not indemnify nor in any way provide protection for  
patent or possible patent violations to its customers or users of it products.  
1.4.3  
Dial Modifier  
Command  
Function  
0 to 9  
Dialing digits  
A, B, C, D, *, #  
Tone dial characters  
Pulse dial  
P
R
Reverse Originate mode  
Dial NVRAM telephone number  
Tone dial  
S=n  
T
W
,
Wait for dial tone  
Pause  
!
Flash hook  
@
;
Wait for quiet answer  
Return to command state  
Ignored by modem  
- ( )  
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AT Command Summary Tables  
AT Command Summary Tables  
2
This section contains summary tables of all AT commands, S-registers, and between AT commands  
and S-registers. These commands are fully described in the relevant sections of the 536EX  
Developers Manual.  
Table 5. Data Mode Command Summary  
Reported  
by &Vn  
Note  
Command  
Function  
Default  
Range  
**  
A/  
A
Repeat last command  
none  
none  
1
no  
Answer  
no  
no  
Cn  
Carrier control option  
Transmit carrier always off  
Normal transmit carrier  
Dial command  
0, 1  
C0  
C1  
D
none  
1
no  
*
En  
Command mode echo  
Disables echo  
0, 1  
yes  
E0  
E1  
Enables echo  
Hn  
In  
Switch hook control  
Hangs up the telephone line  
Picks up the telephone line  
0
0
0, 1  
no  
no  
H0  
H1  
07, 1011,  
14, 2023  
Identification/checksum option  
I0  
I1  
I2  
I3  
I4  
I5  
I6  
I12  
ROM Checksum  
Modem Name  
Manufacturer  
Chipset  
Firmware Version  
Modem Chip Hardware Configuration  
DSP Patch Level  
Country Code  
I7I11, I13,  
I14, I20–  
Reserved  
I25  
*
Ln  
Speaker volume control  
Low speaker volume  
Low speaker volume  
Medium speaker volume  
2
03  
yes  
L0  
L1  
L2  
*
Value saved in NVRAM.  
**  
Command not preceded by an AT.’  
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AT Command Summary Tables  
Table 5. Data Mode Command Summary (Continued)  
Reported  
by &Vn  
Note  
Command  
Function  
Default  
Range  
L3  
High speaker volume  
*
Mn  
Speaker control  
1
03  
yes  
M0  
M1  
M2  
Speaker always off  
Speaker on until carrier present  
Speaker always on  
Speaker off during dialing; speaker on until  
carrier present  
M3  
On  
Go online  
0
0, 1, 3  
no  
O0  
O1  
Returns modem to Data mode  
Retrains equalizer and then returns to Data  
mode  
Renegotiates rate and then returns to Data  
mode  
O3  
*
*
P
Select pulse dialing  
none  
0
yes  
yes  
Qn  
Result code display control  
Enables result codes  
Disables result codes  
Select an S-register  
0, 1  
Q0  
Q1  
Sn  
none  
none  
033  
no  
no  
n = 033  
x = 0255  
Sn=x  
Write to an S-register  
Sn?  
T
Read from an S-register  
Select tone dialing  
none  
none  
1
033  
no  
*
*
no  
Vn  
Result code form  
0, 1  
yes  
V0  
V1  
Choose numeric form  
Choose verbose (text) form  
Response code data rate  
DTE data rate  
*
Wn  
0
04  
yes  
W0, W1  
W2  
Modulation, DCE TX rate  
Modulation, DCE TX rate, Error Correction,  
Compression and DTE data rate  
W3  
W4  
Modulation, DCE TX rate, Error Correction,  
Compression  
*
Value saved in NVRAM.  
** Command not preceded by an AT.’  
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AT Command Summary Tables  
Table 5. Data Mode Command Summary (Continued)  
Reported  
by &Vn  
Note  
Command  
Function  
Default  
Range  
04  
*
Xn  
Result code type  
4
yes  
Enables result codes 04; disables detection  
of busy and dial tone  
X0  
X1  
Enables result codes 05, 10, and above;  
disables busy and dial tone detection  
Enables result codes 06 and 10 and above;  
disables busy detection and enables dial  
tone detection  
X2  
Enables result codes 05, 7, and 10 and  
above; enables busy detection and disables  
dial tone detection  
X3  
X4  
Enables result codes 07 and 10 and above;  
enables busy and dial tone detection  
*
Yn  
Zn  
Long space disconnect  
0
0
1
0, 1  
0, 1  
0, 1  
yes  
no  
Y0  
Y1  
Disables long space disconnect  
Enables long space disconnect  
Recall stored profile  
Z0  
Z1  
Resets modem and recalls user profile 0  
Resets modem and recalls user profile 1  
DCD (data carrier detect) option  
*
&Cn  
&Dn  
yes  
Ignores remote modem status; DCD always  
on  
&C0  
&C1  
DCD set according to remote modem status  
DTR (data terminal ready) option  
2
03  
yes  
&D0  
&D1  
In Async mode, modem ignores DTR  
Modem switches from data mode to  
command mode when an on-to-off transition  
of DTR occurs  
When DTR switches off, the modem goes  
on-hook and disables Auto-answer mode;  
when DTR switches on, auto-answer is  
enabled  
&D2  
&D3  
Turning off DTR re-initializes the modem and  
resets values except UART registers  
&F  
Load factory defaults  
none  
0
no  
Guard tone option (1200 bps and 2400 bps  
only)  
*
&Gn  
02  
yes  
&G0  
&G1  
&G2  
Disables guard tone  
Enables 550 Hz guard tone  
Enables 1800 Hz guard tone  
Select serial flow control  
&Kn  
3
0, 3, 4  
yes  
*
Value saved in NVRAM.  
**  
Command not preceded by an AT.’  
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AT Command Summary Tables  
Table 5. Data Mode Command Summary (Continued)  
Reported  
by &Vn  
Note  
Command  
Function  
Default  
Range  
&K0  
&K3  
&K4  
Disables flow control  
Bidirectional hardware flow control  
XON/XOFF software flow control  
Dial pulse ratio  
*
*
&Pn  
0
0, 1  
yes  
Sets 10 pps pulse dial with 39%/61% make-  
break  
&P0  
&P1  
Sets 10 pps pulse dial with 33%/67% make-  
break  
&Sn  
DSR (data set ready) option  
DSR is always active  
0
0, 1  
yes  
&S0  
&S1  
DSR active only during handshaking and  
when carrier is lost  
&Tn  
&Un  
&Vn  
&Wn  
&Yn  
Self test commands  
0
0
0
0
0
01, 8  
0, 1  
no  
no  
no  
no  
yes  
&T0  
&T1  
Terminates test in progress  
Initiates local analog loopback  
Disable Trellis coding  
*
&U0  
&U1  
Enables Trellis coding with QAM as fallback  
QAM modulation only  
View active and stored profiles  
View active profile and stored profile 0  
View active profile and stored profile 1  
Stored active profile  
0, 1, 3  
0, 1  
&V0  
&V1  
&W0  
&W1  
Store in user profile 0  
Store in user profile 1  
*
Select stored profile on power up  
Recall stored profile 0 on power-up  
Recall stored profile 1 on power-up  
0, 1  
&Y0  
&Y1  
n = 03  
Store telephone number (up to 30 digits) to  
location n(03)  
x = 09 A B  
C D # * T P  
R W @ , ! ;  
&Zn=x  
none  
1
no  
*
*
*
%En  
Auto-retrain control  
Disables auto-retrain  
Enables auto-retrain  
Rate renegotiation  
Disabled  
0, 1  
0, 1  
yes  
%E0  
%E1  
%Gn  
1
yes  
%G0  
%G1  
Enabled  
Value saved in NVRAM.  
** Command not preceded by an AT.’  
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AT Command Summary Tables  
Table 5. Data Mode Command Summary (Continued)  
Reported  
by &Vn  
Note  
Command  
Function  
Default  
Range  
02  
*
-Cn  
Generate data mode calling tone  
Calling tone disabled  
0
no  
-C0  
-C1  
-C2  
1300 Hz calling tone enabled  
V.8 calling tone and 1300 Hz calling tone  
1, 1, C1,  
0, 0  
+A8E=m  
V.8 and V.8 bis operation controls  
Controls break handling  
See note  
no  
no  
no  
+EB  
1, 0, 30 See note  
0, 0, 1, ,  
0, 0, 0,  
+ESA  
Synchronous access mode configuration  
Controls selective repeat option in V.42  
+ESR  
+ETBM  
+GCAP  
+GCI  
1
02  
no  
no  
no  
no  
no  
no  
no  
no  
no  
no  
Controls call termination buffer management 1, 1, 20 See note  
Request complete capabilities list  
Country of installation  
Identify modem manufacturer  
Identify product model  
Identify firmware version  
Identify product serial number ID  
Controls DTE-DCE flow control  
Controls local rate reporting  
Disabled  
none  
none  
none  
none  
none  
none  
2, 2  
+GMI  
+GMM  
+GMR  
+GSN  
+IFC  
See note  
0, 1  
+ILRR=m  
m=0  
0
m=1  
Enabled  
+MA  
Controls modulation automode  
Selects modulation  
See note  
See note  
no  
no  
+MR=m  
m=0  
0
Disabled  
m=1  
Enabled  
V92, 1,  
0, 0, 0, 0  
+MS=m  
Modulation selections  
See note a  
0, 1  
no  
+PCW=m  
+PHSW=m  
+PIG=m  
Call waiting enable  
0
no  
no  
no  
no  
no  
no  
no  
no  
no  
Controls 2C relay  
none  
PCM upstream ignore  
Modem on hold enable  
V.92 modem on hold hook flash  
Initiate modem on hold  
Modem on hold timer  
1
+PMH=m  
+PMHF  
0
none  
+PMHR  
none  
+PMHT=m  
+PQC=m  
+PSS=m  
0
0
2
V.92 phase 1 and phase 2 control  
Use short sequence  
*
Value saved in NVRAM.  
**  
Command not preceded by an AT.’  
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AT Command Summary Tables  
a. For Data mode, the factory default setting is AT+MS=V92, 1, 0, 0, 0, 0 to send at speeds of 33,600 bps or  
below and receive at speeds of 53,333 bps and below.  
Note: See the relevant sections in the 536EX Developers Manual for full command description and  
parameter ranges.  
Table 6. V.44/V.42/V.42 bis MNP Command Summary  
Reported  
by &Vn  
Note Command  
Function  
Default  
Range  
*
*
%An  
%Cn  
Set auto-reliable fallback character  
MNP 5 data compression control  
13  
1
0127  
yes  
0, 1  
yes  
yes  
%C0 No compression  
%C1 Enables MNP5 data compression  
MNP block size  
*
\An  
3
03  
\A0  
\A1  
\A2  
\A3  
Maximum 64 characters  
Maximum 128 characters  
Maximum 192 characters  
Maximum 256 characters  
Set transmit break  
\Bn  
\Cn  
3
0
09  
02  
*
Set auto-reliable buffer  
No data buffering  
yes  
\C0  
\C1  
Four-second buffer until 200 characters in the buffer or  
detection of a SYN character  
No buffering. Connects non-V.42 modems to V.42  
modem  
\C2  
*
*
\Gn  
\Jn  
Set modem port flow control  
Disables port flow control  
Sets port flow control to XON/XOFF  
bps rate adjust control  
Disables rate adjust  
0
0
5
0, 1  
0, 1  
05  
yes  
yes  
no  
\G0  
\G1  
\J0  
\J1  
Enables rate adjust  
\Kn  
Set break control  
Enters command mode,  
connect state, transmits  
no break sent  
\K0  
\K1  
command state, transmits  
Destructive/expedited  
connect state, receives  
connect state, transmits  
command state, transmits Destructive/expedited  
connect state, receives  
*
Value saved in NVRAM.  
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AT Command Summary Tables  
Table 6. V.44/V.42/V.42 bis MNP Command Summary (Continued)  
Reported  
by &Vn  
Note Command  
Function  
Default  
Range  
Enters command mode,  
no break sent  
connect state, transmits  
\K2  
command state, transmits  
connect state, receives  
connect state, transmits  
Nondestructive/expedited  
\K3  
\K4  
\K5  
command state, transmits Nondestructive/expedited  
connect state, receives  
Enters command mode,  
connect state, transmits  
no break sent  
command state, transmits  
Nondestructive/  
nonexpedited  
connect state, receives  
connect state, transmits  
Nondestructive/  
command state, transmits  
nonexpedited  
connect state, receives  
*
*
\T0  
\Xn  
Disables inactivity timer  
0
0
090  
yes  
yes  
Set XON/XOFF pass-through  
Processes flow control characters  
0, 1  
\X0  
Processes flow control characters and passes to local  
or remote  
\X1  
*
*
-Jn  
Set V.42 detect phase  
1
3
0, 1  
yes  
yes  
-J0  
-J1  
Disables the V.42 detect phase  
Enables the V.42 detect phase  
V.42 bis compression control  
Disables V.42 bis  
Hn  
H0  
03  
H1  
H2  
Enables V.42 bis only when transmitting data  
Enables V.42 bis only when receiving data  
Enables V.42 bis for both transmitting and receiving  
data  
H3  
On  
+DR=m  
V.42 bis string length  
32  
0
6250  
no  
no  
Controls data compression reporting  
0, 1  
m=0 Disabled  
m=1 Enabled  
3, 0,  
2048, 6  
*
*
+DS=m  
Controls V.42 bis data compression  
See note yes  
Value saved in NVRAM.  
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AT Command Summary Tables  
Table 6. V.44/V.42/V.42 bis MNP Command Summary (Continued)  
Reported  
by &Vn  
Note Command  
Function  
Default  
Range  
3, 0, 0,  
471,  
942,  
+DS44=m  
V.44 Data Compression  
140,  
no  
140,  
1884,  
3768  
Controls the 32-bit frame check sequence option in  
V.42  
+EFCS  
+ER=m  
0
0
02  
0, 1  
no  
no  
Controls error control reporting  
m=0 Disabled  
m=1 Enabled  
+ES=m Error control selection  
Value saved in NVRAM.  
*
*
3, 0, 2  
See note yes  
Table 7. Fax Identity Command Summary  
Command  
Function  
Default  
none  
Range  
Reported by &Vn  
+FMDL?  
+FMFR?  
+FMI  
Identifies product model  
no  
Identifies modem manufacturer  
Identifies modem manufacturer  
Identifies product model  
none  
none  
none  
none  
none  
no  
no  
no  
no  
no  
+FMM  
+FMR  
Identifies product version number  
Identifies product version number  
+FREV?  
Table 8. Fax Class 1 Command Summary  
Reported  
by &Vn  
Command  
Function  
Default  
Range  
+FCLASS=1 Mode selection  
0
0, 1, 8  
no  
+FRH=m  
+FRM=m  
Receive HDLC data  
Receive data  
none  
3
no  
no  
24, 48, 72, 73, 74, 96, 97, 98, 121, 122,  
145, 146  
none  
+FRS=m  
+FTH=m  
Wait for silence  
none  
none  
1255  
no  
no  
Transmit HDLC data  
3
24, 48, 72, 73, 74, 96, 97, 98, 121, 122,  
145, 146  
+FTM=m  
+FTS=m  
Transmit data  
none  
no  
no  
Stop transmission and pause none  
0255  
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AT Command Summary Tables  
Table 9. IS-101 Voice Command Summary  
Command  
Function  
Voice mode selection  
Default  
Range  
0, 1, 8  
Reported by &Vn  
no  
+FCLASS=8  
+FLO=m  
0
1
Flow Control Select  
Buffer threshold setting  
Caller ID selection  
02  
no  
no  
no  
+VBT=m  
192, 320  
0*  
192, 320  
02  
+VCID=m  
0255,  
0255  
+VDR=m  
Distinctive Ring selection  
0,0  
no  
C’  
BB860980  
BFE63883  
BB863EE0  
+VEM=m  
Event reporting and masking  
no  
+VGM=m  
+VGR=m  
+VGS=m  
+VGT=m  
+VIP  
Speakerphone microphone gain  
Receive gain selection  
128  
121131  
121131  
121131  
121131  
no  
no  
no  
no  
no  
no  
no  
no  
no  
no  
no  
no  
no  
no  
no  
no  
no  
no  
128  
Speakerphone speaker gain  
Volume selection  
128  
128  
Initialize parameter  
+VIT=m  
+VLS=m  
+VNH=m  
+VRA=m  
+VRN=m  
+VRX  
DTE/DCE inactivity timer  
Hardware type control  
0
0255  
015  
0
Automatic hang-up control  
Ringback-goes-away timer  
Ringback-never-appeared timer  
Record mode  
0
02  
50  
050  
10  
0255  
none  
+VSD=m  
+VSM=m  
+VSP=m  
#VSPS=m  
+VTD=m  
+VTS=m  
+VTX  
Silence detection (quiet and silence)  
Compression method selection  
Speakerphone on/off control  
Speakerphone type selection  
Beep tone duration timer  
DTMF and tone generation  
Play mode  
128, 50  
See note  
See note  
0, 1  
140, 8000, 0, 0  
0
1
0, 1  
100  
none  
none  
5255  
See note  
* The noted parameters, commands, and responses depend on the capability to receive.  
Note: See the complete command description in the 536EX Developers Manual for range information.  
Table 10. Voice DTEDCE Character Pairs  
Response  
Hex Code  
00  
Function  
<NUL>  
<DLE>  
<SUB>  
<ETX>  
/
Do nothing  
10  
1A  
03  
2F  
Two contiguous <DLE><DLE> codes indicate a single <DLE> in the data stream  
<DLE><DLE> in data stream  
End transmit data state  
Start of DTMF tone shielding  
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AT Command Summary Tables  
Table 10. Voice DTEDCE Character Pairs (Continued)  
Response  
Hex Code  
7F  
Function  
<DEL>  
DTMF transition to off  
Bump up the volume  
u
75  
64  
1B  
21  
18  
3F  
d
Bump down the volume  
End receive data state  
Receive data abort  
<ESC>  
!
<CAN>  
?
Clear transmit buffer of voice data  
Transmit buffer space available query  
Table 11. Voice DTEDCE Character Pairs  
Response  
<DLE>  
Hex Code  
Function  
10  
1A  
3
Single <DLE> character in the data stream  
<SUB>  
<DLE><DLE> in data stream  
End of Record mode data  
<ETX>  
X
58  
2E  
2F  
7F  
Packet header for Complex Event Detection Report’  
Packet terminator for the Complex Event Detection Report’  
Start of DTMF tone shielding  
DTMF transition to off  
.
/
<DEL>  
09  
AD  
*
3039  
4144  
2A  
23  
DTMF tones 09  
DTMF tones AD  
DTMF tone *  
#
DTMF tone #  
o
6F  
Receive buffer overrun  
c
63  
1100 Hz fax calling tone  
e
65  
1300 Hz data calling tone  
h
68  
Local phone goes on hook  
Local phone goes off hook  
Presumed hang-up silence time-out  
Presumed end-of-message quiet time-out  
Loop current interruption  
H
s
48  
73  
q
71  
I
6C  
4C  
72  
L
Loop current polarity reversal  
Ringback  
r
b
62  
Busy/reorder/fast busy  
d
64  
Dial tone detected  
u
75  
Transmit buffer under-run  
p
70  
Line voltage increase (extension phone goes on-hook)  
Line voltage decrease (extension phone goes off-hook)  
Fax or data answer tone (2100 Hz)  
P
a
50  
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AT Command Summary Tables  
Table 11. Voice DTEDCE Character Pairs (Continued)  
Response  
Hex Code  
Function  
f
66  
52  
Data answer detected (2225 Hz)  
Incoming ring  
R
% (,)  
25, 26, 27, 28, 29 Manufacturer-specified  
Table 12. Dial Modifiers  
Command  
Function  
0 to 9  
Dialing digits  
A, B, C, D, *, #  
Tone dial characters  
Pulse dial  
P
R
Reverse Originate mode  
Dial NVRAM telephone number  
Tone dial  
S=n  
T
W
,
Wait for dial tone  
Pause  
!
Flash hook  
@
;
Wait for quiet answer  
Return to command state  
Ignored by modem  
- ( )  
Table 13. S-Register Summary  
Note Register  
Function  
Default  
Range  
0255  
Units  
Reported by &Vn  
*
S0  
No. of rings to auto-answer on  
Ring count  
0
ring  
ring  
yes  
yes  
yes  
yes  
yes  
yes  
yes  
yes  
yes  
yes  
yes  
yes  
S1  
0
0255  
0127  
0127  
0127  
*
S2  
Escape character  
43  
13  
10  
8
ASCII  
ASCII  
ASCII  
S3  
Carriage return character  
Line feed character  
Backspace character  
Wait before dialing  
Wait for carrier  
S4  
S5  
032, 127 ASCII  
*
*
*
*
*
*
*
*
S6  
2
2255  
1255  
0255  
1255  
1255  
50255  
0255  
second  
second  
second  
0.1 second  
0.1 second  
ms  
S7  
60  
2
S8  
Pause time for dial modifier  
Carrier recovery time  
Lost carrier hang up delay  
DTMF dialing speed  
Guard Time  
S9  
6
S10  
S11  
S12  
S14  
14  
70  
50  
138  
(0.02 second) yes  
no  
Bit-mapped options  
* Value saved in NVRAM.  
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AT Command Summary Tables  
Table 13. S-Register Summary (Continued)  
Note Register  
Function  
Default  
Range  
Units  
Reported by &Vn  
S16  
Modem test options  
Modem test timer  
0
no  
*
*
*
*
*
*
S18  
S21  
S22  
S25  
S30  
S33  
0
0255  
second  
yes  
no  
Bit-mapped options  
Bit-mapped options  
Detect DTR change  
Disconnect inactivity timer  
Sleep mode timer  
48  
118  
5
no  
0255  
0255  
090  
0.01 second  
minute  
second  
yes  
yes  
yes  
0
10  
* Value saved in NVRAM.  
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Data Mode AT COMMANDS  
Data Mode AT COMMANDS  
3
The 536EX chipsets implement:  
Standard Hayes*-compatible AT commands and S-registers in data mode  
Standard EIA/TIA-578 AT commands in Class 1 fax mode  
Additional AT command sets for error correction, data compression and voice mode  
In data mode, the AT commands configure the DCE (modem) to establish a connection with a  
remote data modem. In data mode, the 536EX chipsets execute the AT commands for error  
correction (MNP 2-4, V.42) and data compression (MNP 5, V.42 bis) described in Table 21 on  
page 57, as well as the fax and voice mode commands AT+FCLASS=1 (fax) and AT+FCLASS=8  
(voice).  
3.1  
Using AT Commands to Access the S-Registers  
[Sn?, Sn=x, ?]  
The DTE can access the S-registers through the ATSn?, ATSn=x, and ? commands. For example,  
to configure the modem to automatically answer a data modem call after two rings, type ATS0=2.  
Examples:  
ATS0=2  
ATS0?  
ATS0=  
AT?  
Configures S-register S0 to ‘2’  
Reads the contents of S-register S0  
Configures S-register S0 to ‘0’  
Reads the contents of the last accessed (read or write) S-register  
3.2  
Modem Responses and Command Echo [En, Vn, Xn,  
Wn, Qn]  
The ATEn command configures the DCE to send back to the DTE any data that the DTE sent to  
the DCE while in command mode. The ATVn command sets the DCE response codes to either text  
or numeric form. For example, upon successfully processing an AT command string, the DCE  
sends an OK(text) or a 0(numeric) to the DTE.  
Examples:  
Host  
Command  
Modem Setup  
Modem Response  
AT<CR>0<CR>  
Echo, Numeric (E1, V0)  
AT<CR>  
ATS0?<CR> ATS0?<CR>000<CR><LF>0<CR>  
AT<CR> AT<CR><CR><LF> OK<CR><LF>  
Echo, Text (E1, V1)  
ATS0?<CR> ATS0?<CR><CR><LF>000<CR><LF><CR>  
<LF>OK<CR><LF>  
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Data Mode AT COMMANDS  
Host  
Command  
Modem Setup  
Modem Response  
No Echo, Numeric (E0, V0) AT<CR>  
ATS0?<CR> 000<CR><LF>0<CR>  
AT<CR> <CR><LF>OK<CR><LF>  
0<CR>  
No Echo, Text (E0, V1)  
ATS0?<CR> <CR><LF>000<CR><LF><CR><LF>OK  
<CR><LF>  
The DCE can be configures to use different response codes depending on the V.250 command that  
is enabled (AT+MR, AT+ER, AT+DR, and AT+ILRR). Alternatively, the ATWn command can  
be used to set these V.250 commands. The mapping for the ATWn command to V.250 commands  
is shown in Table 14. The setting for the ATXn command (page 43) can affect which ATWn  
response codes are reported to the DCE. The ATXn command configures the modem call progress  
detection and reporting requirements during dialing (for example, dial tone and busy tone  
detection). The ATQn command selects whether the modem sends result codes to the DTE.  
Table 14. Data Reporting Wn Mapping  
Wn  
+ER  
Disable  
+DR  
Disable  
+MR  
Disable  
+ILRR  
Disable  
W0  
W2  
W3  
W4  
Disable  
Enable  
Enable  
Disable  
Enable  
Enable  
Enable  
Enable  
Enable  
Enable  
Enable  
Disable  
For example, a connection is established with the remote modem as shown below (with LAPM  
error correction and V.42 bis data compression). The telephone line (or modem-to-modem  
connection) data rate is 33,600 bps and the local UART (DTE-to-modem) connection rate is  
115,200 bps.  
Figure 3. Example of a Remote Connection  
Telephone  
UART  
Line  
Interface  
LOCAL MODEM  
REMOTE MODEM  
DTE  
(33,600 bps)  
(115,200 bps)  
The modem then sends the CONNECTmessages for the following four Wn commands:  
ATW0  
ILRR: 115200  
CONNECT 50666  
ATW2  
+MCR: V90  
+MRR: 28800  
CONNECT 50666  
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Data Mode AT COMMANDS  
ATW3  
+MCR: V90  
+MRR: 28800  
+ER: LAPM  
+DR: V42B  
+ILRR: 115200  
CONNECT 50666  
ATW4  
+MCR: V90  
+MRR: 28800  
+ER: LAPM  
+DR: V42B  
CONNECT 50666  
3.3  
Modem Reset and NVRAM Commands [DS=m, Zn,  
&F, &Vn, &Yn, &Wn, &Zn=x]  
On powering-up, the DCE defaults to the configuration specified in NVRAM. The DCE may then  
be configured as needed. The DTE stores the DCE configuration in the NVRAM by first setting up  
the current configuration and then sending an AT&Wn command. The DCE configuration stored  
in the NVRAM is called a user profile. Two independent user profile configurations and four  
telephone numbers can be stored. Either user profile configuration can be used for the power-up  
defaults (AT&Yn). While in command mode, the DCE can be re-initialized at any time and the  
user profile changed using the ATZn command. To configure the modem to factory defaults, the  
AT&F command is used. A summary of the active user profile, two NVRAM user profiles, and  
previously-saved telephone numbers can be read from the modem using the view command,  
AT&Vn. The AT&Zn=x command stores one of four telephone numbers in the NVRAM. To dial  
these telephone numbers, use the ATDS=m command.  
If the active profile is not stored in one of the two user profiles after setting up the modem, then the  
current settings are lost when the commands ATZ or AT&F are issued or when the modem is  
powered down.  
Examples:  
ATZ  
Resets and then configures the modem to NVRAM user profile 0.  
AT&F S0=1 &W1  
&Y1  
&F configures the modem for factory defaults.  
S0=1 configures the modem to answer after one ring.  
&W1 saves the active configuration to user profile 1.  
&Y1 configures the modem to use NVRAM user profile 1 as the  
power-up defaults.  
AT&Z2 = 9,  
Stores a telephone number into the NVRAM as phone number 2, which  
(408)444-5555  
can be re-dialed later using ATDS=2.  
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Data Mode AT COMMANDS  
3.4  
Modem Identification Commands [In, +FMI, +FMR,  
+FMM, +GMI, +GMM, +GMR, +GSN,  
+FMFR?, +FMDL?, +FREV?]  
The modem provides product identification AT commands that help determine the modems  
manufacturer, model number, and product revision. To provide flexibility with older software  
application programs, the modem supports several commands that can be used to request a single  
item of identification (such as a modem model number). Table 15 lists the commands used to  
obtain product information (all identification commands are usable in data, fax, or voice mode).  
Table 15. Product Identification Information  
AT Commands  
Product Information  
ATIn Command  
Data Mode  
Class 1 Fax Mode  
Legacy Modems  
Modem Manufacturer  
Model ID  
ATI2  
ATI1  
ATI4  
AT+GMI  
AT+GMM  
AT+GMR  
AT+FMI  
AT+FMM  
AT+FMR  
AT+FMFR?  
AT+FMDL?  
AT+FREV?  
Revision Number  
Example:  
ATI1  
Causes the modem to send the modems name to the DTE.  
Intel 536EP  
V.92 Modem  
Response to the modem name request.  
3.5  
Establishing a Modem Connection [A, D, DS = n, S0]  
Data mode provides several methods for establishing a connection with a remote modem. For each  
modem, a connection can be initiated manually or automatically in both answer and originate  
modes. A manual-to-manual connection is useful when both modems (that are on-hook) are  
connected to an off-hook telephone line. For example, if two people are talking on the telephone,  
they can manually establish a modem connection without first hanging up. When establishing a  
manual connection, one modem must be designated as the originating modem and the other as the  
answering modem. Manual originate mode is initiated by sending an ATD to the DCE. Manual  
answer mode is accomplished by sending an ATA to the DCE.  
Automatic originate mode is initiated by sending an ATD <telephone number & dial modifiers>  
or ATDS=m to the DCE. Automatic-answer mode is accomplished by setting S-register S0 to a  
non-zero value. S1 keeps track of how many ring signals are detected. If the content of S0 is non-  
zero and the number of ring signals (as defined by S0) are detected (that is, S1 = S0), then the DCE  
goes off-hook and attempts to connect to the remote modem (with the following exceptions):  
The time period between the ring signals is greater than 8 seconds, which causes the S1  
counter to reset and thus never reach the value for S0.  
Caller ID is enabled and S0=1, the modem answers on the second ring signal instead of the  
first ring signal. This happens because Caller ID puts a signal on the telephone line between  
the first and second ring signal.  
Example:  
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Data Mode AT COMMANDS  
ATDT 9,444-5555 Automatically dials the telephone number with DTMF tones. After  
dialing a 9, the comma (,) causes the modem to pause two seconds  
before dialing the rest of the telephone number.  
modem 1: ATD;  
modem 2: ATA  
When establishing a manual-to-manual connection, the designated  
originating modem should receive the ATD command from its DTE  
just before the designated answering modem receives the ATA  
command from its DTE. It is important that the time between the ATD  
and ATA commands is less than 2 seconds.  
AT-C1DT 123  
Causes the modem to dial the telephone number 123 and immediately  
start sending a data calling tone. Calling tone can then be detected by  
the remote voice mail system. After detecting the calling tone, the  
remote system can change to data mode and start the data modem  
connection handshake.  
3.6  
Online Command Mode [Escape Codes, On]  
After establishing a connection with a remote modem, the DTE sends the appropriate escape  
sequence to the DCE, which causes the DCE to enter the online command mode. The online  
command mode is used to send AT commands to the DCE while the DCE is still connected to the  
remote modem. The supported escape sequences are described in Section 3.10, AT Escape  
Sequenceson page 38. To re-enter the online data mode, use the ATOn command.  
Example:  
1 second +++  
1 second  
Hayes Escape Sequence. Guard times (in which the DTE does not send  
data to the DCE) of 1 second are needed before and after the three  
escape characters +.  
+++AT<CR>  
ATO  
TIES (Time Independent Escape Sequence).  
Causes the modem to re-enter online data mode.  
3.7  
Hanging Up [Hn, S10, Zn, &D2]  
A modem connection terminates when the modem hangs up or when the remote modem transmit  
carrier is off longer than the duration specified in S-register S10. To hang up, the DTE typically  
sends an escape code sequence that causes the DCE to enter online command mode. Upon  
receiving an OKmessage, the DTE sends either ATH or ATZn to the DCE. When the AT&D2  
command is used, the modem goes on-hook (hangs up) after an on-to-off transition of the DTR  
occurs.  
Note: The ATZn command causes the DCE to hang up and re-initialize itself to the user profile specified  
by n.  
3.8  
Modem-to-Modem Connection Data Rates  
The data rates differ for each data mode selected. The 536EX chipsets either default to V.90 or V.92  
mode depending on the driver version. For non-ISP connections, the chipsets fall back to V.34  
mode. The modem defaults to whatever mode is issued by the +MS=m command (see the  
supported modulation types on Table 16 on page 35).  
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Data Mode AT COMMANDS  
In Data mode, the 56K chipsets can transmit up to 48,000 bps (V.92 mode) or 33,600 bps (V.90  
mode) and receive up to 53,333 bps. Note that the chipsets are capable of achieving 56,000 bps, but  
power limitations by the FCC limit actual speeds to 53,333 bps. The 56K receive data rates can be  
achieved only in connections with equipment-compatible ISPs (Internet Service Providers). In V.92  
mode, the 536EX supports three new features: Quick Connect, Modem-on-Hold and Pulse Code  
Modulation (PCM) Upstream.  
The Quick Connect (QC) feature reduces the time it takes to make a connection to your service  
provider. The modem retains information of the line conditions from your previous connection and  
uses this information to bypass parts of the training sequence. As a result, this provides faster  
connections. Normal V.90 connections take about 2530 seconds. With V.92 Quick Connect, your  
connect times can be up to 50% faster.  
The V.92 Quick Connect feature is controlled by the +PSS and +PQC commands. The +PQC  
command enables and disables the shorten phase 1 and or phase 2 startup procedures. The +PSS  
command forces either a short or full startup procedure on the next and subsequent connections. To  
enable the modem for V.92 Quick Connect, set +PSS=0 or 1 and +PQC=0. Refer to Table 5 for the  
detailed description of these commands.  
The Modem-on-Hold (MOH) feature allows you to receive an incoming voice call and stay  
connected to the Internet and then return online after your conversation without having to re-dial.  
This is very convenient where the same phone line is used for voice calls and data connections. To  
receive an incoming call as described above requires that you have the Call-Waiting service from  
your telephone company. In addition, the Caller ID service from your telephone company is  
recommended but not required for MOH. This feature allows you to determine who is calling. The  
holdtime for your incoming call is define by your service provide. The MOH feature also allows  
you put you data connection on hold and initiate a voice call and then return online after  
completing your voice conversation. These two scenarios are described in detail in Figure 4 and  
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Data Mode AT COMMANDS  
Figure 4. Modem-on-Hold: Incoming Voice Call in Data Mode  
Enable MOH  
(+PMH=0)  
(+PCW=0)  
Enable Caller ID  
(Optional)  
(+VCID=1)  
Incoming Call  
HW Ring Indication  
(+++AT)  
Accept Call  
Accept/Reject  
Call  
?
Request to go  
on hold  
(+PMHR)  
Reject Call  
Stay Online  
(ATO)  
Server  
Accepts  
Request  
?
No (Returns 0)  
No  
Yes  
(Returns 1-13)  
Disconnect  
?
Flash Hook  
(+PMHF)  
Yes  
End Data Connection  
Answer Call  
Finish Call  
(ATH)  
Flash Hook  
(+PMHF)  
Go Back Online  
(ATO)  
A9111-01  
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Data Mode AT COMMANDS  
Figure 5. Modem-on-Hold: Initiating a Voice Call in Data Mode  
Enable MOH  
(+PMH=0)  
Command Mode  
(+++AT)  
Request to go  
on hold  
(+PMHR)  
Server  
Accepts  
No (Returns 0)  
Request  
?
Yes  
(Returns 1-13)  
No  
Disconnect  
?
Flash Hook  
(+PMHF)  
Yes  
Initiate Call  
End Data Connection  
(ATH)  
Finish Call  
Flash Hook  
(+PMHF)  
Go Back Online  
(ATO)  
A9112-01  
The following sequence describes how to configure the modem for MOH to process an incoming  
voice call while online. First, MOH must be enabled. The +PMH and +PCW commands are used  
to enable MOH and to capture the Call Waiting tone which is sent when the voice call comes in. To  
enable MOH, set +PMH=0 and +PCW=0. Next, to enable Caller ID information (optional), by  
setting +VCID=1. Now the modem is configured for the incoming call. When you receive the  
incoming call, the modem will get a ring indication and the software/application will issue a  
+++AT to put the modem in command mode. Then, you will be prompted to either Acceptor  
Rejectthe call based on the Caller ID information (if enabled). If you reject the call, an ATO  
command is issued to perform a Quick Connect to stay online. If you accept the call, the data  
connection is put on hold, and the modem send a request to the server to go on hold using the  
+PMHR command. The server will accept enable (113 returned) or reject (0 returned) the  
request. If the server accepts the request to go on hold, the modem issues the +PMHF to flash the  
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Data Mode AT COMMANDS  
hook to connect the call. Now you can answer the phone and talk. After completing your voice  
conversation, the modem will issue another +PMHF and ATO command to initiate a Quick  
Connect. If the server rejects the request to go on hold, the user can stay on line (ATO command  
issued) or disconnect from his initial data connection (ATH command issued).  
The next sequence describes how to initiate a voice call while online. First, enable the MOH  
feature by setting +PMH=0. When online, the user can initiate a voice call by first issuing +++AT  
to put the modem in command mode. Then request the server to go on hold by issuing the +PMHR  
command. The server will either accept (113 returned) or reject (0 returned) the request. If the  
server accepts the request to go on hold, the modem issues the +PMHF to flash the hook and get  
dial tone. You can then make a voice call. After completing the voice conversation, the modem will  
issue another +PMHF and ATO command to initiate a Quick Connect. If the server rejects the  
request to go on hold, the user can stay on line (ATO command issued) or disconnect from his  
initial data connection (ATH command issued). Refer to Table 5 for the detailed description of the  
V.92 commands.  
The PCM Upstream feature allows you to upload data to the network up to 48,000 bps. This is an  
improvement over the 33,600 bps maximum with V.90. This is beneficial when you are sending  
large file, email attachments and gaming on the Internet. The +PIG command is used to enable and  
disable the PCM Upstream feature. To enable PCM Upstream, set +PIG=0. To disable PCM  
Upstream, set +PIG=1.  
Several V.34 modes are available (see Table 16). These provide different speeds. For example,  
V34S offers a modem-to-modem data rate of 2400, 4800, 7200, 9600, 12,000, 14,400, 16,800,  
19,200, 21,600, 24,000, 26,400, and 28,800 bps. For V.42, MNP, and Buffer (Normal) modes, the  
modem provides speed buffering (see Section 4 starting on page 56), which allows the DTE-to-  
modem data rate to be different from the modem-to-modem data rate. Users can take advantage of  
this feature by setting the DTE-to-modem rate to a high speed like 115,200 bps and letting the  
modem negotiate the best line rate.  
The 536EX chipsets can be configured (by the +MS=m command) to support either asymmetrical  
or symmetrical connections. The modem transmits and receives at the same speed in symmetrical  
connections and at different speeds in asymmetrical mode. V.90 and V.92 connections are always  
asymmetrical. V.34 mode connections can be either symmetrical or asymmetrical. The modem uses  
six parameters for asymmetrical modes and four parameters for symmetrical modes. Note that the  
transmitter speed and receiver speeds typically are different for most V.34 connections over the  
PSTN.  
To configure the DTE-to-modem data rate (in data on-hook command mode), change the terminal  
program COM port speed selection or write the appropriate divisor latch values for a given speed  
to the UART Divisor Latch registers. Then send an AT<CR>or any other valid AT command to the  
modem. The modem responds with an OKat the new data rate. All commands and modem  
responses that follow use the new data rate.  
Note: In command mode, the modem only changes its DTE-to-modem data rate after the Divisor Latch  
register values change and the DTE sends a valid AT command.  
The +MS=m command defines which modem-to-modem data rates are supported by the modem.  
The table below shows the supported modulation types. Each modulation supports one or more  
data rates. Refer to page 53 for the +MS command description.  
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Data Mode AT COMMANDS  
Table 16. Supported Modulation Types  
<carrier >  
Description  
Bell 103  
300 bps  
Bell 212A 1200 bps  
V21  
V.21 300 bps  
V22  
V.22 1200 bps  
V22B  
V23C  
V32  
V.22 bis 1200 and 2400 bps  
V.23, with constant carrier; 1200 bps forward and 75 bps reverse  
V.32 4800 and 9600 bps  
V32B  
V.32 bis 7200, 9600, 12,000, and 14,400 bps  
V.34 asymmetrical connections: 2400, 4800, 7200, 9600, 12,000, 14,400, 16,800, 19,200,  
21,600, 24,000, 26,400, 28,800, 31,200, and 33,600 bps  
V34  
V90  
56K V.90 asymmetrical connections (transmit): 4800, 7200, 9600, 12,000, 14,400, 16,800,  
19,200, 21,600, 24,000, 26,400, and 28,800, 31,200, and 33,600 bps  
56K V.90 asymmetrical connections (receive): 28,000, 29,333, 30,666, 32,000, 33,333, 34,666,  
36,000, 37,333, 38,666, 40,000, 41,333, 42,666, 44,000, 45,333, 46,666, 48,000, 49,333,  
50,666, 52,000 53,333, 54,666, and 56,000 bps  
56K V.92 asymmetrical connections (transmit): 24,000, 25,333, 26,666, 28,000, 29,333, 30,666,  
32,000, 33,333, 34,666, 36,000, 37,333, 38,666, 40,000, 41,333, 42,666, 44,000, 45,333, 46,666  
and 48,000 bps  
V92  
56K V.92 asymmetrical connections (receive): 28,000, 29,333, 30,666, 32,000, 33,333, 34,666,  
36,000, 37,333, 38,666, 40,000, 41,333, 42,666, 44,000, 45,333, 46,666, 48,000, 49,333,  
50,666, 52,000, 53,333, 54,666, and 56,000 bps  
If the +MS=m parameters contain conflicting information like +MS=V34,1,14400,0with a DTE  
data rate of 2400 bps, then the modems connection attempts always fail, and the modem reports a  
NO CARRIERmessage. This happens because when the modem receives the +MS=m  
command, the modem does not check for conflicts of valid parameter information.  
Table 17 shows the resulting connection data rate when using non-default values. Because of  
impairments on the telephone line, the actual connection speeds may be lower than the speeds  
defined in this table.  
For V.92, V.90, and V.34 modulation, the modem can receive data at a different data rate than the  
transmit data rate. All other modulation types besides V.23 and V.34 use the same data rate for the  
transmitter and receiver. Use ATW3 to see the modems actual receive and transmit data rates (the  
modem must be configured for ATV1 text response codes). Table 17 shows examples of the  
resulting connection rate when non-default values are used.  
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Data Mode AT COMMANDS  
Table 17. Resulting Modem-to-Modem Connection Rates with Non-Default Values  
Originating Modem  
Answering Modem  
Resulting Connection Speed  
+MS = V34, 1, 0, 0, 0,  
0;  
the UART data rate =  
115,200 bps  
+MS = V32, 1, 0, 9600, 9600 bps: the originating modem is configured to attempt  
0, 0;  
a maximum 28,800 bps connection, but the answering  
modem is configured to attempt a maximum data rate of  
9600 bps.  
the UART data rate =  
14,400 bps  
+MS = V34, 0, 33,600,  
33,600, 0, 0;  
+MS = V32B, 1, 0,  
9600, 0, 0;  
No connection: the originating modem is configured to  
attempt only a 33,600 bps connection, but the answering  
UART data rate =  
115,200 bps  
B1 and UART data rate modem is configured to attempt a maximum data rate of  
= 14,400 bps  
9600 bps.  
9600 bps: the originating modem is configured to attempt  
+MS = V34, 1, 0,0, 0, 0; connection at between 7200 to 9600 bps or below. The  
+MS = V32,  
1, 7200, 9600, 0, 0;  
and UART data rate =  
7200 bps  
UART data rate =  
9600 bps  
answering modem is configured to attempt a data rate of  
9600 bps or below. The connection takes place at  
7200 bps, the highest speed supported by both modems.  
3.9  
3.9.1  
36  
Diagnostic Testing [S18, &Tn]  
The &Tn command initiates loopback tests. Setting S-register S18 to a non-zero value determines  
the length of testing after the modem receives the &Tn command. After the testing period elapses,  
the modem halts the test and returns to command mode. To abort the test before the test timer has  
timed out, enter the escape code sequence followed by AT&T0. Setting S18 to an 0disables the  
test timer. In this case, the loopback test continues to run until an escape code, followed by AT&T0  
(or ATH), is sent to the modem.  
The modem provides a local analog loopback test (see Section 3.9.1, Local Analog Loopback  
[AT&T1]on page 36) for testing modem-to-modem integrity in all modes except V.90 and V.92.  
After entering the loopback mode, the communication integrity is checked by the DTE sending  
data to the modem and then checking the looped-back data for errors. In addition, in the self-test  
mode the modem implements an internal data pattern generator and checker that detects errors.  
When a data error occurs in self-test mode, the modem increments an internal error counter. Upon  
completing the test, the modem sends a three-digit error count to the DTE. These tests are  
illustrated in the following examples.  
Local Analog Loopback [AT&T1]  
This test is used by the local DTE to check the DTE-to-modem communication integrity. The local  
DTE will not initiate the test from online command mode.  
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Data Mode AT COMMANDS  
Figure 6. Local Analog Loopback Test  
LOCAL MODEM  
TXD  
TRANSMITTER  
RECEIVER  
DTE  
RXD  
Local Modem (or Test Modem)  
AT&F &W<CR>  
Returns the modem to the factory defaults.  
AT S18 = 0 &T1 Causes the modem to run local analog loopback without self-test.  
CONNECT 115200 Modem response code indicates that analog loopback is  
enabled with a DTE speed of 115200.  
This is a test.Test string that the user could type at the keyboard. If the received data  
is the same as the test string, then the DTE-to-modem communication  
channel is working properly.  
+++AT  
OK  
TIES Escape Sequence is used to return to command mode.  
Modem enters command mode.  
AT&T0  
OK  
Terminates any loopback test.  
Modem aborts analog loopback and stays in command mode.  
3.9.2  
Local Analog Loopback With Self-Test [AT&T8]  
This test is used by the local DTE to check the DTE-to-modem communication integrity.  
Figure 7. Local Analog Loopback with Self-Test  
LOCAL MODEM  
TXD  
PATTERN  
GENERATOR  
TRANSMITTER  
RECEIVER  
DTE  
RXD  
PATTERN  
CHECKER  
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Data Mode AT COMMANDS  
Local Modem (or Test Modem)  
AT&F &W<CR> Returns the modem to the factory defaults.  
AT S18=20 &T8 Causes the modem to start local analog loopback with self-test for 20  
seconds.  
OK  
After starting analog loopback, the modem goes back to command  
mode.  
AT  
OK  
The modem responds to new commands.  
000  
OK  
After 20 seconds, the modem stops analog loopback, sends  
an error count to the DTE, and enters command mode.  
AT S18=0 &T8  
Causes the modem to start local analog loopback with self-test, which  
is only terminated by AT&T0 or ATH.  
OK  
After starting analog loopback, the modem goes back to command  
mode.  
AT  
OK  
The modem responds to new commands.  
AT&T0  
000  
OK  
After receiving AT&T0 or ATH, the modem stops analog  
loopback, sends an error count to the DTE, and enters  
command mode.  
3.10  
AT Escape Sequences  
The 56K family provides the industry-standard Time Independent Escape Sequence (TIES). The  
DTE sends the escape sequence to return the modem to command state while in the online data  
state (that is, connected to another modem) or in diagnostic mode (&Tn commands).  
Intel also makes the HayesEscape Sequence available to customers; however, see the following  
statement regarding licensing requirements.  
Licensing Requirements for Hayes Escape Sequence  
The Intel chipsets are manufactured with TIES as the default setting. It is Hayesposition that you  
must either have or obtain a valid license from Hayes Microcomputer Products, Inc., of Norcross,  
Georgia, before producing modem systems that use the Hayes Escape Sequence.  
Intel accepts no responsibility and does not indemnify nor in any way provide protection for  
patent or possible patent violations to its customers or users of its products.  
3.10.1  
Time-Independent Escape Sequence  
The TIES (Time-Independent Escape Sequence), implemented with +++AT, was developed by a  
group of modem manufacturers as an alternative to the Hayes Escape Sequence. TIES was  
designed for compatibility with existing communication software written for the Hayes Escape  
Sequence.  
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Data Mode AT COMMANDS  
The DTE implements the escape sequence by sending the escape character (as defined in S2) three  
times, followed by a valid AT command, and then the contents of S3 (typically a <CR>). Upon  
detecting the three consecutive escape characters, the modem changes to TIES command mode and  
starts an internal EPD (Escape Prompt Delay) timer (with the time limit defined by S12). The  
modem then looks for one of the following conditions to occur:  
No additional data is received and the EPD timer times out: the modem sends an OK’  
message to the DTE and then waits indefinitely for an incoming valid AT command string  
from the DTE. Until the modem receives a valid AT command, it monitors any data received  
from the DTE and passes on the data to the remote modem (that is, the modem does not echo  
back the received character to the DTE).  
If the subsequent character received by the modem is not an Aor a, the modem returns  
to data mode and sends a CONNECTmessage back to the DTE.  
If the modem receives an Aor a, it stores any additional data received from the DTE in  
the modems internal command buffer and continues to send the data to the remote  
modem. The modem then waits until the DTE sends a <CR>, or up to 39 data characters,  
before deciding whether to go to command mode or to return to data mode. Upon  
detecting a <CR> or receiving the 39 data characters, the modem determines if a valid AT  
command has been received. If a non-AT command string or an invalid command string  
has been received, then the modem changes back to data mode and sends a CONNECT’  
message to the DTE. If a valid AT command has been received, the modem changes to  
command mode and sends an OKmessage. After sending the OKmessage, the modem  
echoes any received data from the DTE while in command mode.  
An ‘A’ or ‘a’ is received from the DTE. The modem disables the EPD timer and sends the  
character to the remote modem. The modem then stores any received data from the DTE into  
the modem internal command buffer and sends the data to the remote modem. Upon detecting  
a <CR> or receiving up to 39 data characters, the modem determines if a valid AT command  
has been received; if so, it processes the valid commands. If a non-AT command string or an  
invalid command string has been received, then the modem remains in data mode. If a valid  
AT command has been received, then the modem changes to command mode and sends an  
OKmessage. After sending this, the modem (while in command mode) echoes back any data  
received from the DTE.  
Any character except an Aor ais received from the DTE. The modem disables the EPD  
timer and changes back to data mode.  
If an AT command string is received while in TIES command mode, the modem processes any  
valid AT command. Upon detecting an invalid AT command, the modem changes back to data  
mode and issues a CONNECTmessage to the DTE. While in TIES command mode, the modem  
ignores certain characters that may cause the modem to incorrectly decide that an incoming AT  
string is invalid. The ignore characters are <LF>, <space>, and <CR> (<CR> is ignored only when  
S3 is not equal to <CR>). Not all AT commands are supported during TIES command mode. The  
following is a list of supported commands:  
En, Hn, Mn, On, Qn, Sn, Vn, Xn, and &commands (except &Tn and &F)  
The escape character is determined by the value stored in S-register S2, and it is typically a +’  
character. The following is an example of the TIES Escape Sequence:  
Format:  
<char1><char2><char3><AT command><contents of S3>  
char1 = char2 = char3 = escape character (S2)  
Example:  
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Data Mode AT COMMANDS  
DTE:  
DCE:  
+++ AT<CR>  
OK  
Note: TIES requires that the three-character escape sequence be contiguous and not repeated. The  
character immediately preceding the first character of the three-character sequence cannot be the  
same as the escape character. Therefore, +++ AT<CR>is valid, but ++++ AT<CR>is not.  
3.10.2  
Hayes* Escape Sequence  
In this escape sequence, implemented with +++, the DTE sends the modem an escape character  
three times, preceded and followed by guard times. Upon detecting the escape sequence, the  
modem sends an OKresponse to the DTE. To re-enter the online data state, the DTE then sends  
the modem ATO followed by the contents of S-register S3 (typically a <CR>).  
The escape character is determined by the value stored in S-register S2 and is typically a +’  
character. Guard times are silence times when the DTE does not send any data to the modem.  
Guard times ensure that the modem does not falsely detect an escape sequence if three consecutive  
escape characters are received from the DTE. The preceding and following guard times are defined  
in S-register S12. Typically, these guard times are 1 second. In addition to the preceding and ending  
guard times, there are inter-character time-outs between each escape character sent. The inter-  
character time-outs define the maximum amount of time allowed between characters before the  
modem ignores the previous escape characters. This inter-character delay time is set to 1 second.  
An example of the Hayes Escape Sequence follows:  
Format:  
<gt1><char1><tm 2><char2><tm3><char3><gt4>  
gt1 = gt4 preceding and following guard times (S12)  
tm2 = tm3 inter-character time-out (= 1 second)  
char1 = char2 = char3 = escape character (S2)  
Example:  
DTE:  
1 second +++ 1 second  
OK  
DCE:  
Table 18. Data Mode Command Descriptions  
Command Default  
Description  
Repeat Last Command: This command re-executes the last AT command string stored in the command  
buffer. A/ is the only command not preceded by AT and ended by a carriage return.  
A/  
none  
Sending any character (such as a carriage return) after A/ and before a modem response is sent to the  
DTE causes the modem to abort the remainder of the command string in the modem internal command  
buffer.  
Answer Command: This command causes the modem to immediately go off-hook and initiate an  
answer mode handshake without waiting for an incoming ring signal. This command is useful for  
manually answering a call or establishing a back-to-back connection with an originate-mode modem.  
A
none  
1
Carrier Control Option: This command is reserved for selecting between controlled carrier or constant  
carrier modes. This modem supports only constant carrier mode.  
Cn  
n = 0  
Transmit carrier always off (returns an ERROR message)  
Normal transmit carrier (constant carrier)  
n = 1*  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Dial Command: This command causes the modem to immediately go off-hook as an originating modem  
and dial a telephone number with corresponding dial modifiers. Dial modifiers are parameters that define  
how the modem should dial the telephone number.  
Dial Modifiers  
09  
Dialing Digits  
A, B, C,  
D, *, #  
P
Tone Dial Characters  
Pulse Dialconfigures the modem to use pulse dialing to dial a telephone number.  
R
Reverse Originate Modeplaces the modem in answer mode. This modifier should be the  
last character in the dialing string (for example, ATDT 12345678R). After dialing the  
telephone number, the modem goes into data modem answer mode instead of originate  
mode.  
S = n  
Dial NVRAM Telephone Numbercauses the modem to dial a telephone number  
previously stored in the NVRAM with the AT&Zn=x command.  
D
none  
T
Tone Dialconfigures the modem to use DTMF tones to dial a telephone number.  
W
Wait for Dial Tonecauses the modem to look for dial tone for a specified amount of time.  
If dial tone or the amount of time specified by the S-register, S6, times out, the modem  
processes the next command in the dial string. If a busy signal is detected, the modem  
responds to the DTE with a busy response code and then goes into off-line command  
mode.  
,
Pausecauses the modem to pause or delay implementing the next parameter in the dial  
string by the time specified in S-register S8.  
!
Flash Hookcauses the modem to go on-hook for 0.75 seconds.  
@
Wait for Quiet Answercauses the modem to wait for specified amount of time (S-register  
S7) followed by 5 seconds of silence before processing the next dial modifier.  
;
Return to Idle Statecauses the modem to enter online command mode without initiating a  
data modem handshake (used for phone directory auto-dialers).  
<space> - ( ) Ignored by Modemthese four characters are ignored by the modem. Spaces also may be  
included in the dial string to separate area codes and numbers.  
Command Mode Echo: This command selects whether the modem echoes AT commands back to the  
host in either online or off-line command mode.  
En  
Hn  
1
0
n = 0  
Echo disabled  
Echo enabled  
n = 1*  
Switch Hook Control: This command controls the telephone line relay (OHREL*) and causes the  
modem to either hang up or pick up the telephone line.  
n = 0*  
n = 1  
Hang up telephone line (go on-hook)  
Pick up telephone line (go off-hook)  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Identification/Checksum Option: This command causes the modem to send product code and  
hardware setup information to the DTE.  
n = 0*  
n = 1  
n = 2  
n = 3  
n = 4  
n = 5  
n = 6  
n = 12  
ROM Checksum  
Modem name  
Manufacturer  
Chipset  
Firmware version  
Modem chip hardware configuration  
DSP patch level  
Country code  
In  
0
n = 711,  
13, 14,  
2025  
Reserved  
Example:  
ATI2  
Intel Corporation  
OK  
Speaker Volume Control: This command selects the modems speaker volume.  
n = 0  
n = 1*  
n = 2  
n = 3  
Low speaker volume  
Low speaker volume  
Medium speaker volume  
High speaker volume  
Ln  
2
Speaker Control: This command specifies when the speaker is turned on and off.  
n = 0  
n = 1*  
n = 2  
n = 3  
Speaker always off  
Mn  
On  
1
0
Speaker on until carrier present  
Speaker always on  
Speaker off during dialing, and on until carrier  
Go Online: This command causes the modem to return back to online data mode from online command  
mode.  
n = 0*  
n = 1  
n = 3  
Returns the modem to data mode  
Begins an equalizer retrain sequence; then returns to data mode  
Renegotiates rate and then returns to data mode  
Select Pulse Dialing: This command configures the modem to use pulse dialing next time the modem  
dials a telephone number.  
P
none  
0
Result Code Display Control: This command selects whether the modem sends result codes to the  
DTE.  
Qn  
n = 0*  
n = 1  
Result codes enabled  
Result codes disabled  
Select an S-Register: This command selects the current S-register.  
n = 033  
Sn  
none  
none  
none  
Write to an S-Register: This command writes a decimal number xto S-register n.  
Sn=x  
n = 033  
x = 0255  
Read an S-Register: This command is used to read a decimal number from S-register n.  
n = 033  
Sn?  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Select Tone Dialing: This command configures the modem to use DTMF tones the next time the  
modem dials a telephone number (touch tone dialing).  
T
none  
1
Result Code Form: This command selects whether the modems basic syntax response codes are in  
numeric or verbose form.  
Vn  
n = 0  
Numeric form  
Text form  
n = 1*  
Response Code Data Rate: This command selects whether the modem sends the DTE independent  
modem connection extended syntax result codes for modulation mode, speed, error control protocol, or  
data compression before the final 'CONNECT' message. This command does the selection by enabling  
and disabling the appropriate V.250 reporting commands (+MR, +ER, +DR, and +ILRR).  
n = 0*, 1  
CONNECT result code reports DTE speed.  
For example:  
+ILRR: 115200  
CONNECT 50666  
n = 2  
CONNECT result code reports modulation mode and DCE transmitter speed.  
For example:  
+MCR: V90  
+MRR: 28800  
CONNECT 50666  
n = 3  
CONNECT result code reports DTE data rate, modulation mode, error correction, data  
compression, DCE transmitter speed and DCE receiver speed.  
Wn  
0
For example:  
+MCR: V90  
+MRR: 28800  
+ER: LAPM  
+DR: V42B  
+ILRR: 115200  
CONNECT 50666  
n = 4  
CONNECT result code reports modulation mode, error correction, data compression, DCE  
transmitter speed and DCE receiver speed.  
For example:  
+MCR: V90  
+MRR: 28800  
+ER: LAPM  
+DR: V42B  
CONNECT 50666  
Please refer to +MR=m, +ER=m, +DR=m and +ILRR=m for a detailed description of each  
command.  
Result Code Type/Call Progress: This command determines which modem result codes are enabled.  
Additionally, this command specifies whether busy and dial tone detection are enabled or disabled.  
n = 0  
n = 1  
n = 2  
Result codes 04 enabled. Busy and dial tone detect disabled.  
Result codes 05, 10 and above enabled. Busy and dial tone detect disabled.  
Xn  
4
Result codes 06, 10 and above enabled. Busy detect disabled and dial tone detect  
enabled.  
n = 3  
Result codes 05, 7, 10 and above enabled. Busy detect enabled and dial tone detect  
disabled.  
n = 4*  
Result codes 07, 10 and above enabled. Busy and dial tone detect enabled.  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Long Space Disconnect: This command determines whether the modem disconnects after receiving  
1.6 seconds of silence and whether the modem sends a period of silence to the remote modem before  
disconnecting.  
Yn  
0
n = 0*  
n = 1  
Disables long space disconnect  
Enables long space disconnect. The modem disconnects after receiving 1.6 seconds of  
silence from the remote modem. Additionally, after receiving an ATH0 command, the  
modem sends at least 4 seconds of silence before hanging up.  
Reset Modem/Recall Stored Profile: This command causes the modem to go on-hook (hang-up),  
perform a warm reset, and load user-configuration profile n(previously stored in the NVRAM) into the  
active profile. The Zn command must be the last command in command string, as it causes all  
subsequent commands to be ignored.  
Zn  
0
1
n = 0*  
n = 1  
Resets the modem and recalls user profile 0  
Resets the modem and recalls user profile 1  
DCD (Data Carrier Detect) Option: This command controls how the modem functions in relation to the  
DCD or RLSD signal.  
&Cn  
n = 0  
State of carrier from remote modem is ignored. DCD is always on.  
n = 1*  
State of carrier from remote modem is tracked. DCD reflects the state of the received  
carrier.  
DTR (Data Terminal Ready) Option: This command controls how the modem responds to DTR. After  
toggling DTR, the host should wait 200 ms before modifying the UART registers or sending a new  
command to the modem. This is done because the modem does not send an OKmessage to indicate it  
has performed the requested function.  
n = 0  
n = 1  
In asynchronous mode (&Q0), the modem ignores DTR.  
The modem switches from data mode to command mode when an on-to-off transition of  
DTR occurs.  
&Dn  
2
n = 2*  
n = 3  
An on-to-off transition of DTR causes the modem to go on-hook (hang up). While DTR is  
off, auto-answer is disabled.  
An on-to-off transition of DTR re-initializes the modem. The re-initialize procedure performs  
the same function as a power-up reset, except that the UART registers are not  
reconfigured.  
Load Factory Defaults: This command loads command defaults and S-register factory defaults into the  
active configuration and configures the modem for data mode.  
&F  
none  
Guard Tone Option: This command controls whether the modem sends out guard tones while  
connected to a remote modem (for ITU-T V.22 bis [1200 bps] and V.22 bis [2400 bps] connections only).  
Guard tones may be required in some countries but are not needed in the United States. Guard tones are  
sent by the answer modem to disable Central Office echo cancelers.  
&Gn  
0
n = 0*  
n = 1  
n = 2  
Guard tone disabled  
550 Hz guard tone enabled  
1800 Hz guard tone enabled  
Select Serial Port Flow Control: This command specifies the DTE-to-modem flow control. Software  
flow control uses the characters XOFF (13h) and XON (11h) to stop and start data transmission,  
respectively, both to and from the DTE. Bidirectional hardware flow control uses RTS/CTS to stop and  
start data from the modem.  
&Kn  
3
n = 0  
n = 3*  
n = 4  
Disables flow control  
Bidirectional hardware flow controlRTS/CTS  
XON/XOFF software flow control  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Dial Pulse Ratio: This command determines the make/break (that is, off-hook/on-hook) ratio during  
pulse dialing.  
&Pn  
&Sn  
0
0
n = 0*  
n = 1  
Make = 39%; Break = 61% at 10 pulses per secondfor use in the United States.  
Make = 33%; Break = 67% at 10 pulses per secondfor use in the United Kingdom and  
Hong Kong.  
DSR (Data Set Ready) Option: This command controls how the modem treats the DSR signal.  
n = 0*  
n = 1  
DSR circuit always on  
DSR circuit is on during handshaking, off in test or idle modes. DSR is off when the carrier  
is lost.  
Data Mode Self-Test Command: This command is used in data mode (except x2 and V.90 connections)  
to initiate and terminate loopback tests for testing modem-to-modem and DTE-to-modem data  
communication integrity.  
&Tn  
&Un  
0
0
n = 0*  
n = 1  
n = 8  
Terminates test in progress  
Local analog loopback  
Local analog loopback with self-test  
Disable Trellis Coding: This command selects whether the modem transmits or receives modulated  
9600 bps carrier with QAM or Trellis encoding for V.32.  
n = 0*  
n = 1  
Enabled (Trellis modulation with QAM modulation as a fallback)  
Disabled (QAM modulation only)  
View Active Configuration and Stored Profiles: This command causes the modem to display the  
command and S-register information contained in the active user profile and in one of two stored  
profiles.The command &V0 displays the active profile and the stored profile 0; &V1 displays the active  
profile and the stored profile 1. The information in the active profile is stored into the user profiles with the  
&Wn command. &W0 stores the active profile into the stored profile 0; &W1, the stored profile 1.  
n = 0*  
n = 1  
Stored profile 0  
Stored profile 1  
AT&V0  
ACTIVE PROFILE:  
E1 L2 M1 T Q0 V1 W0 X4 Y0 &C1 &D2 &G0 &J0 &K3 &P0 &S0 &Y0  
%A013 %C1 %E1 \A3 \C0 \G0 \J0 \T000 \X0 -J1  
S00:000 S01:000 S02:043 S03:013 S04:010 S05:008 S06:002 S07:060 S08:002  
S09:006 S10:014 S11:070 S12:050 S18:000 S25:005 S27:064 S32:032 S33:010  
+ES=003,000,002 +DS=003,000  
&Vn  
0
STORED PROFILE 0:  
E1 L2 M1 T Q0 V1 W0 X4 Y0 &C1 &D2 &G0 &J0 &K3 &P0 &S0  
%A013 %C1 %E1 \A3 \C0 \G0 \J0 \T000 \X0 -J1  
S00:000 S02:043 S06:002 S07:060 S08:002 S09:006 S10:014 S11:070 S12:050  
S14:138 S18:000 S21:048 S22:118 S23:048 S25:005 S27:064 S30:000 S32:032  
S33:010 +ES=003,000,002 +DS=003,000  
TELEPHONE NUMBERS:  
&Z0 =  
&Z2 =  
&Z1 =  
&Z3 =  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Store Active Profile: This command causes the modem to store a subset of the active profile command  
and S-register configurations into the NVRAM user profile n.  
&Wn  
&Yn  
0
0
n = 0*  
n = 1  
Store in user profile 0  
Store in user profile 1  
Select Stored Profile on Power-up: This command selects the particular stored user profile from the  
NVRAM to be loaded into the active profile upon modem power-up.  
n = 0*  
n = 1  
Select profile 0  
Select profile 1  
Store Telephone Number: This command stores a telephone number up to 30 digits (including dial  
modifiers) in the NVRAM. To dial the stored telephone number, use the ATDS=m command. Use the &V  
command to see the stored telephone number.  
&Zn=x  
%En  
none  
n = 03  
x = 09 A B C D # * T P R W @ , ! ;  
Auto-Retrain Control: This command controls whether the modem automatically initiates a modem  
retrain whenever the received data signal quality falls below a threshold that may affect data reliability.  
The value for nis stored in the NVRAM.  
1
1
n = 0  
Disabled  
Enabled  
n = 1*  
Rate Renegotiation: This command selects whether the modem automatically initiates a change to a  
higher speed or lower speed depending on received signal quality (that is, rate negotiation). The modem  
always responds to any rate change initiated by the remote modem.  
%Gn  
n = 0  
Disabled  
Enabled  
n = 1*  
Generate Data Modem Calling Tone: This command allows the DTE to select whether the modem  
sends a 1300 Hz calling tone or V.8 calling tone when originating a data modem connection.  
n = 0*  
n = 1  
n = 2  
Calling tone disabled  
-Cn  
0
1300 Hz calling tone sent for all data modem connections  
V.8 calling tone sent for V.34 modulation and 1300 Hz calling tone sent for all other  
modulations  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
V.8 and V.8 bis Operation Controls: This command configures V.8 and V.8 bis operation. If issued  
when the DCE is on-hook, this command is a compound parameter used to precondition V.8 and V.8 bis  
originating and answering operation. It is not supported as an action command while the DCE is off-hook.  
If enabled, V.8 negotiation does not preclude simultaneous implementation of other means of negotiation  
(for example, V.8 bis, V.18, and V.32 bis Annex A).  
For the +A8E default values, the signal indicators are not generated by the DCE. When the parameters  
<v8o>=6 and <v8a>=5, the +A8I, +A8C, +A8A, +A8J, and +A8M indications are sent from the DTE, but  
the +A8M command is not used because the DCE controls the V.8 section.  
m = <v8o>, <v8a>, <v8cf>, <v8b>,<cfrange>, <protrange>  
Defaults: 1, 1, C1, 0, ,  
<v8o> V.8 origination selection.  
Range: 0, 1, 6  
0
Disable V.8 origination negotiation  
1*  
6
DCE-controlled V.8 origination negotiation  
DCE-controlled V.8 origination negotiation, enable indications only  
<v8a> V.8 answer selection.  
Range: 0, 1, 5  
0
Disable V.8 answer negotiation  
1*  
5
DCE-controlled V.8 answer negotiation  
DCE-controlled V.8 answer negotiation, enable indications only  
<v8cf> V.8 call function  
+A8E=m  
see m’  
Range: 0x21, 0xC1  
0x21  
Sets the V.8 call function to indicate H.324.  
Sets the V.8 call function to indicate standard data mode.  
0xC1*  
<v8b> V.8 bis control  
Range: 0  
0*  
Disable V.8 bis negotiation  
<cfrange> Not supported.  
<protrange> Not supported.  
Indication  
Definition  
Indicates V.8 ANSam has been detected. This indication is only sent to the DTE if  
+A8E<v8o>=6 and operating in originate mode.  
Indicates V.25 answer tone (2100 Hz) has been detected. This indication is only sent to  
the DTE if +A8E<v8o>=6 and operating in originate mode.  
Indicates the detection of a V.8 CI-signal and the recovered call function (only if  
+A8E<v8a>=5 and operating in answer mode).  
Indicates the hexadecimal-coded CM signal (only if +A8E<v8a>=5 and operating in  
answer mode)  
Indicates the hexadecimal-coded JM signal (only if +A8E<v8o>=6 and operating in  
originate mode)  
+A8A:1  
+A8A:2  
+A8I:<v8cf>  
+A8M:<CM>  
+A8M:<JM>  
Indicates the modem is transmitting the V.8 termination signal. +A8J:1 indicates  
+A8J:[0,1] transmission or detection of CJ while +A8J:0 indicates time-out while waiting for a CJ  
signal.  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Break Handling: Controls break handling in error control operation. It accepts three numeric  
subparameters:  
Syntax:  
+EB = <break selection>, <timed>, <default length>  
<break selection> specifies the type of break to be signaled to the remote DCE upon detecting one from  
the local DTE.  
0
1
2
3
Ignore Break (do not signal to remote DCE)  
Non-expedited, non-destructive  
Expedited, non-destructive  
+EB  
1, 0, 30  
Expedited and destructive  
<timed> specifies if the break signal to be signaled to the remote DCE is timed or not.  
0
1
Sent without a break signal length  
Sent with break signal length  
<default length> specifies the amount of time in tens of milliseconds that a break should be signaled to  
the local DTE when an indication of a break is received from the remote DCE without explicitly indicated.  
0
1
Do not deliver received break to DTE  
Default break length 0.01 to 2.54 seconds. Used for default to signal DTE when break  
received from the remote DCE without break length  
Controls the use of breaks in V.42.  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Synchronous Access Mode Configuration: controls the manner of operation of the Synchronous Access  
Mode in the DCE (if present).  
Syntax:  
+ESA=[<trans_idle>[,<framed_idle>[,<framed_un_ov>[,<hd_auto>[,<crc_type>[,<nrzi_en>[,<syn1>[,<sy  
n2>]]]]]]]]  
<trans_idle> specifies the bit sequence transmitted by the DCE when a transmit data buffer underrun  
condition occurs, while operating in Transparent sub-Mode.  
0
1
2
In Transparent sub-Mode, DCE transmits 8-bit SYN sequence on idle. DCE receiver does  
not hunt for synchronization sequence  
In Transparent sub-Mode, DCE transmits 8-bit SYN sequence on idle. DCE receiver hunts  
for 8-bit SYN sequence  
In Transparent sub-Mode, DCE transmits 16-bit SYN sequence on idle. DCE receiver hunts  
for 16-bit SYN sequence  
<framed_idle> specifies the bit sequence transmitted by the DCE when a transmit data buffer underrun  
condition occurs immediately after a flag, while operating in Framed sub-Mode.  
0
1
In Framed sub-Mode, DCE transmits HDLC flags on idle  
In Framed sub-Mode, DCE transmits marks (ones) on idle  
<framed_un_ov> specifies the actions undertaken by the DCE when a transmit data buffer underrun or  
overrun condition occurs immediately after a non-flag octet, while operating in Framed sub?Mode.  
0
1
In Framed sub-Mode, DCE transmits abort on underrun in middle of frame  
In Framed sub-Mode, DCE transmits a flag on underrun in middle of frame, and notifies  
DTE of underrun or overrun  
<hd_auto> specifies whether or not, in V.34 half duplex operation, additional procedures besides those  
0, 0, 1, specified in clause 12/V.34 shall be performed by the DCE when switching from primary channel to  
, 0, 0,  
secondary channel operation, and vice versa.  
0,  
0
1
When switching between primary and secondary channel operation in V.34 half duplex, the  
DCE only executes those procedures defined in clause 12/V.34  
When switching between primary and secondary channel operation in V.34 half duplex, the  
DCE executes additional procedures as described in 8.8.5 besides those defined in clause  
12/V.34  
<crc_type> specifies the CRC polynomial used while operating in Framed sub-Mode.  
0
1
CRC generation and checking disabled  
In Framed sub-Mode, the 16-bit CRC specified in 8.1.1.6/V.42 is generated by the DCE in  
the transmit direction, and checked by the DCE in the receive direction  
2
In Framed sub-Mode, the 32-bit CRC specified in 8.1.1.6/V.42 is generated by the DCE in  
the transmit direction, and checked by the DCE in the receive direction  
<nrzi_en> specifies if Non Return to Zero Inverted (NRZI) encoding is to be used by the DCE for transmit  
and receive data.  
0
1
NRZI encoding and decoding disabled  
NRZI encoding enabled in the DCE in the transmit direction, and NRZI decoding enabled in  
the DCE in the receive direction  
<syn2> specifies the octet value(s) to be used while performing character-oriented framing.  
0255  
When <trans_idle>=0, specifies the 8-bit transmit idle sequence to be used by the DCE.  
When <trans_idle>=1, specifies the 8-bit synchronization sequence to be used by the DCE.  
When <trans_idle>=2, specifies first 8 bits of 16-bit synchronization sequence to be used  
by the DCE  
<syn1> specifies the octet value(s) to be used while performing character-oriented framing.  
0255  
When <trans_idle>=2, specifies last 8 bits of 16-bit synchronization sequence to be used  
by the DCE  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Selective Repeat: Controls the use of selective repeat (SREJ) option in V.42.  
0
1
2
Do not use SREJ  
+ESR  
1
Use SREJ if available in remote DCE; continue without it if not  
Use SREJ if available in remote DCE; disconnect if SREJ is not available  
Call Termination Buffer Management: Controls the handling of data remaining in the DCE buffers upon  
call termination. It accepts three numeric parameters:  
Syntax:  
+ETBM = <pending TD>, <pending RD>, <timer>  
<pending TD> controls how previously transmitted data remaining in the DCE buffers should be handled  
when the local DTE requests disconnection of the call.  
0
1
Discard all buffered data immediately and disconnect  
Attempt until all data is delivered and acknowledged (ignoring timer); if remote DCE  
disconnects discard remaining data  
2
Attempt until all data is delivered and acknowledged; if timer expires or remote DCE  
disconnects, discard remaining data  
+ETBM  
1, 1, 20  
<pending RD> controls how previously received data remaining in the DCE buffers should be handled  
when the remote DCE disconnects the call.  
0
1
Discard all buffered data immediately and disconnect  
Attempt until all data is delivered (ignoring timer); if local DTE requests disconnect discard  
remaining data  
2
Attempt until all data is delivered; if timer expires or local DTE requests disconnect discard  
remaining data  
<timer> sets a maximum time limit that the DCE will attempt to deliver the buffered data before  
disconnecting and discarding the remaining  
030  
Delivery timer value in seconds  
Request Complete Capabilities List: This extended-format command causes the DCE to transmit a list  
of additional capabilities commands.  
AT+GCAP  
+GCAP  
none  
+GCAP: +FCLASS,+MS,+ES,+DS  
OK  
Identify Country of Installation: This extended command is used to indicate and select the country of  
installation for the DCE. The DTE may use this value to determine country-specific functions. To  
determine what countries the DCE supports, issue the AT+GCI=? command. Refer to the ITU-T T.35  
recommendation for the details on what country code is used for each country.  
+GCI=m  
see m’  
Default: country of installation  
m = country code, e.g., United States  
AT+GCI=B5  
Identify Modem Manufacturer: This command causes the DCE to send a message to the DTE  
indicating the DCE manufacturer. This command is identical to AT+FMFR? and AT+FMI.  
AT+GMI  
+GMI  
none  
none  
Intel Corporation  
OK  
Identify Product Model: This command causes the DCE to report the modem chipset name. This  
command is identical to AT+FMDL? and AT+FMM commands.  
AT+GMM  
+GMM  
Intel 536EP V.92 Modem  
OK  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Identify Product Revision: This command causes the DCE to report the modem chipset revision level.  
This command is identical to AT+FREV? and AT+FMR. The response message depends on the  
firmware version.  
+GMR  
none  
none  
AT+GMR  
536EP Release 4.28 - Dec 10 2001  
OK  
Request Product Serial Number Identification: This command causes the DCE to transmit a message  
to the DTE indicating the product serial number identification.  
Syntax:  
AT+GSN  
+GSN  
+GSN: PCI\VEN_8086&DEV_1040&SUBSYS_00000000&REV_00  
OK  
The modem responds with the hardware Id key from the registry that contains the VendorID, SubVendor  
Id, Subsystem VendorId, Device ID, and hardware revision.  
DTE-DCE Local Flow Control: Controls the flow control between local DTE and DCE when V.42 error  
control or normal mode (buffering mode or speed matching) is being used. In addition to acting locally  
the flow control characters can be passed on to remote DCE to act upon. It accepts two numeric  
subparameters:  
<DCE_by_DTE> specifies the method to be used by the DTE to control the flow of received data from  
the DCE; and  
<DTE_by_DCE> specifies the method to be used by the DCE to control the flow of transmitted data from  
the DTE.  
<DCE_by_DTE>  
+IFC  
2, 2  
0
1
2
3
none  
DC1/DC3 software flow control; do not pass DC1/DC3 characters to the remote DCE  
RTS/CTShardware flow control  
DC1/DC3 software flow control with DC1/DC3 characters being passed to the remote DCE  
in addition to being acted upon for local flow control  
<DTE_by_DCE>  
0
1
2
None  
DCI/DC3 software flow control  
RTS/CTS hardware flow control  
DTE to DCE Local Rate Reporting: Controls whether the +ILRR:result code is transmitted from the  
DCE to the DTE once a connection has been made. If enabled the result code displayed shall represent  
the current negotiated DTE-DCE rate, and is issued after any Modulation (+MR:), Error Control (+ER:) or  
Data Compression (+DR:) reports and before the final result code CONNECT. +ILRR accepts one  
numeric parameter decimal value and the format is as follows:  
+ILRR=m  
0
0
1
Disables reporting of local port rate (no +ILRR intermediate result code transmitted)  
Enables reporting of local port rate (+ILRR intermediate result code transmitted)  
Example response message when +ILRR = 1,  
+ILRR: 19200  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Modulation Automode Control: This command specifies the alternative to the preferred modulation  
specified in the +MS=<carrier> command. Alternative modulations are only available when  
+MS=,<automode> enables automode. The alternative modulations available for the +MA command are  
limited to all modulations the modem supports below the preferred modulation specified by  
+MS=<carrier>. The +MA parameters are reset to all modulations supported by the modem below the  
preferred modulation whenever the +MS=<carrier> changes the preferred modulation. The order of  
priority of alternative modulations is determined by such mechanisms as V.8 and PN2330, not the order  
in which they were entered for this command. <carrier> values omitted are no available as alternative  
modulations.  
m= <carrier>,<carrier>,<carrier>  
Defaults: all modulations below +MS=<carrier> and allowed by the DCE limits in the +MS command  
+MA=m  
none  
<carrier> specifies the alternative modulations that are available. A table of these modulations are given  
in +MS command description.  
+MA? will display a list of enabled alternative modulations  
+MA=? will display a list of available alternative modulations. This list is determined by the current values  
of the +MS parameters for preferred modulation, automode and DTE rate limits. For example:  
If +MS=<V32B>, V.34, V.90, and V.92 will not be available because they are above V.32 bis.  
If +MS = ,0,, no alternative modulations will be available.  
If +MS=V34,1,4800,33600, V.22 bis will not be available because its maximum DCE bit rate is  
2400bps.  
Modulation Reporting Control: Controls whether the +MCR: and +MRRresult codes are transmitted  
from the DCE to the DTE once a connection has been made. If enabled the result code displayed shall  
represent the current negotiated DCE-DCE modulation and rate, and are issued before the Error Control  
(+ER:) or Data Compression reports (+DR:) and before the final result code CONNECT. The format is  
as follows:  
0
Disables reporting of modulation (no +MCR and +MRR intermediate result code  
transmitted)  
+MR=m  
0
1
Enables reporting of modulation (+MCR and +MRR intermediate result code transmitted)  
Example if +MR = 1  
+MCR: V34  
+MRR: 33600  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Modulation Selection: This command sets the preferred modulation, whether alternative modulations  
can be tried, and the transmit and receive DCE bit rates.  
m = <carrier>,<automode>,<min rate>,<max rate>,<min rx rate>, <max rx rate>  
Defaults: m = V92,1,0,0,0,0  
+MS? will display the current +MS parameter settings  
+MS=? will display the +MS parameter settings supported by the modem  
<carrier> specifies the preferred modulation. The following table contains the modulations supported.  
<carrier>  
BELL103  
BELL212  
V21  
Description  
Bell 103 300bps (FSK)  
Bell 212A (DPSK)  
V.21 300bps (FSK)  
V22  
V.22 1200bps (QAM)  
V22B  
V.22 bis 1200 or 2400bps (QAM)  
V.23 1200bps forward and 75bsp reverse channel (FSK)  
V.32 4800 or 9600bps (QAM) or 9600bps (TCM)  
V.32 bis 4800 or 9600bps (QAM) or7200, 9600, 12000 or 14400bsp (TCM)  
V23C  
V32  
V32B  
V34  
V.34 2400, 4800, 7200, 9600, 12000, 14400, 16800, 19200, 21600, 24000, 26400, 28800,  
31200 or 33600bps  
V90  
V92  
V.90 4800, 7200, 9600, 12000, 14400, 16800, 19200, 21600, 24000, 26400, 28800, 31200  
or 33600 bps on the transmit channel and 28000, 29333, 30666, 32000, 33333, 34666,  
36000, 37333, 38666, 40000, 41333, 42666, 44000, 45333, 46666, 48000, 49333, 50666,  
52000, 53333, 54666 or 56000 bps (PCM) on the receive channel  
V.92 24000, 25333, 26666, 28000, 29333, 30666, 32000, 33333, 34666, 36000, 37333,  
38666, 40000, 41333, 42666, 44000, 45333, 46666 and 48000 bps on the transmit channel  
and 28000, 29333, 30667, 32000, 33333, 34667, 36000, 37333, 38667, 40000, 41333,  
42667, 44000, 45333, 46667, 48000, 49333, 50667,52000, 53333, 54667 or 56000 bps  
(PCM) on the receive channel  
+MS=m  
see m’  
<automode> enables or disable automatic modulation negotiation. Automatic modulation negotiation  
allows the modem to connect with an alternative modulation to the preferred modulation. Alternative to  
the preferred modulations are specified by the +MA command. The +MA parameters are reset to all  
modulations supported by the modem below the preferred modulation whenever the +MS=<carrier>  
changes the preferred modulation.  
Range: 0, 1  
Default: 1  
<automode> = 0 Disable automatic modulation negotiation  
<automode> = 1 Enable automatic modulation negotiation  
<min rate> and <min rx rate> specifies the lowest bit rate, in decimal units of bits/s, that may be  
established on the DCE. If 0, they are determined by the modulation selected by <carrier>, <automode>  
and the +MA command. These values are reset to 0 whenever +MS=<carrier> changes the preferred  
modulation. <min rx rate> is only used for modulations that support unequal minimum bit rate limits for  
the transmit and receive channel like V.23 and V.90 and is used to specify limits for the receive channel  
as distinct from the transmit channel.  
Range: 0 and the DCE bps given in the <carrier> description table above  
Default: 0  
<max rate> and <max rx rate> specifies the highest bit rate, in decimal units of bits/s, that may be  
established on the DCE. If 0, they are determined by the modulation selected by <carrier>. These values  
are reset to 0 whenever the +MS=<carrier> changes the preferred modulation. <max rx rate> is only  
used for modulations that support unequal maximum bit rate limits for the transmit and receive channel  
like V.23 and V.90 and is used to specify limits for the receive channel as distinct from the transmit  
channel.  
Range: 0 and the DCE bps given in the <carrier> description table above  
Default: 0  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Call Waiting Enable: This command controls the action to be taken upon detection of call waiting in a  
V.92 DCE.  
0
1
2
Toggle V.24 Circuit 125 and collect Caller ID if enabled by +VCID  
+PCW=m  
0
Hang up  
Ignore V.92 call waiting  
This command causes the DCE to activate/de-activate the hook relay for supporting the 2C relay.  
+PHSW=  
m
none  
1
0
1
connects the telco terminals to the modem  
connects the telco terminals to the phone terminals  
PCM Upstream Ignore: This command controls the use of PCM upstream in a V.92 DCE.  
+PIG=m  
0
1
Enable PCM upstream  
Disable PCM upstream  
Modem on Hold Enable: This command controls whether or not modem on hold procedures are  
enabled during V.92 operation.  
+PMH=m  
0
0
1
Enables V.92 modem on hold  
Disables V.92 modem on hold  
V.92 Modem on Hold Hook Flash: This command causes the DCE to go on-hook for a specified period  
of time, and then return on-hook. The specified period of time is normally one-half second, but may be  
governed by national regulations. If this command is initiated and the modem is not On Hold, ERROR is  
returned. This command applies only to V.92 Modem on Hold.  
+PMHF  
none  
Initiate Modem on Hold: This command requests the DCE to initiate or to confirm a modem on hold  
procedure. The DCE shall return ERROR if Modem on Hold is not enabled or if the DCE is in an idle  
condition. The DCE shall return the string response +PMHR: <value> where <value> is a decimal value  
corresponding to the Modem on Hold timer value received or the request status during the DCEs  
modem on hold exchange procedure as defined below. This response may be delayed depending upon  
the context under which the +PMHR command is made, i.e., if the +PMHR is in response to an incoming  
Modem on Hold or if it is initiating a request.  
<value>  
Description  
0
V.92 Modem on Hold Request Denied or not available  
MOH with 10 second time-out Granted  
MOH with 20 second time-out Granted  
MOH with 30 second time-out Granted  
MOH with 40 second time-out Granted  
MOH with 1 minute time-out Granted  
MOH with 2 minute time-out Granted  
MOH with 3 minute time-out Granted  
MOH with 4 minute time-out Granted  
MOH with 6 minute time-out Granted  
MOH with 8 minute time-out Granted  
MOH with 12 minute time-out Granted  
MOH with 16 minute time-out Granted  
MOH with indefinite time-out Granted  
1
2
3
+PMHR  
none  
4
5
6
7
8
9
10  
11  
12  
13  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Data Mode AT COMMANDS  
Table 18. Data Mode Command Descriptions (Continued)  
Command Default  
Description  
Modem on Hold Timer: This command controls whether or not the modem will grant or deny a Modem  
on-hold (MOH) request as well as setting the Modem-on-Hold-Time-Out.  
0
Deny V.92 Modem-on-hold Request  
Grant MOH with 10 second time-out  
Grant MOH with 20 second time-out  
Grant MOH with 30 second time-out  
Grant MOH with 40 second time-out  
Grant MOH with 1 minute time-out  
Grant MOH with 2 minute time-out  
Grant MOH with 3 minute time-out  
Grant MOH with 4 minute time-out  
Grant MOH with 6 minute time-out  
Grant MOH with 8 minute time-out  
Grant MOH with 12 minute time-out  
Grant MOH with 16 minute time-out  
Grant MOH with indefinite time-out  
1
2
3
4
5
+PMHT=m  
0
6
7
8
9
10  
11  
12  
13  
V.92 Phase 1 and Phase 2 Control: This command controls the global enabling or disabling of the V.92  
shortened Phase 1 and Phase 2 startup procedures, not the initiation thereof. This command is used in  
conjunction with the +PSS command.  
0
1
2
3
Enable Short Phase 1 and Short Phase 2  
Enable Short Phase 1  
+PQC=m  
0
Enable Short Phase 2  
Disable short Phase 1 and Short Phase 2  
Use Short Sequence: This command causes a calling DCE to force either a V.92 short or full startup  
sequence as defined by the +PQC command on the next and subsequent connections.  
0
1
2
The DCEs decide whether or not to use the short startup procedures. The short startup  
procedures shall only be used if enabled by the +PQC command.  
+PSS=m  
2
Forces the use of the short startup procedures on the next and subsequent connections if  
they are enabled by the +PQC command.  
Forces the use of the full startup procedures on the next and subsequent connections  
independent of the setting of the +PQC command.  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Error Correction and Data Compression  
Error Correction and Data  
Compression  
4
The 536EX chipsets support two types of data mode error correction (MNP 24 and V.42) and data  
compression (V.44, MNP 5, and V.42 bis). V.42 error correction uses LAPM as the primary error-  
control protocol and uses MNP 2-4 as an alternative. V.44 provides enhanced data compression  
over the existing V.42 bis standard. Data compression is up to on average 40% faster than previous  
methods. This provides for faster web browsing and data downloading. The +DS44 command  
configures the operation of V.44. There are nine parameters associated with the +DS44 command.  
For a detailed description of this command, refer to Table 6. V.42 bis data compression requires  
V.42 (LAPM only). MNP 5 requires MNP 2-4.  
The 536EX chipsets support four operating modes: buffer (normal), MNP reliable, V.42 auto-  
reliable, and V.42 reliable. They allow the DCE to communicate with remote modems that may or  
may not support error correction and data compression. Speed buffering, which is used for all  
operating modes, allows the DTE-to-modem data rate to be different from the modem-to-modem  
data rate. This is accomplished by using transmitter and receiver buffers in the modem. Thus, the  
DTE-to-modem data rate can be set for 2400 bps when the modem-to-modem data rate is 300 bps  
without causing any data errors. In all data modes, the DTE-to-modem data rate can be set for any  
valid speed between 300 bps to 115,200 bps (that is, the modem autobauds up to 115,200 bps). See  
Table 1 on page 11 for all DTE-to-DTE data rates. The modem-to-modem data rates are listed in  
Table 2 on page 11. See Table 3 on page 11 for the modem-to-ISP data rates. Each operating mode  
is explained in more detail in the following tables.  
Table 19. Operating Modes  
Mode  
Features  
Buffer (Normal)  
+ES=1, 0, 1  
No error correction/data compression, but speed buffering is supported.  
MNP Reliable  
MNP 25 connection only. If an MNP connection cannot be established, the modem  
+ES=4, 4, 6  
hangs up.  
V.42 Auto-Reliable  
+ES=3, 0, 2  
V.42/V.42 bis with fallback to MNP 25 or normal mode.  
V.42 Reliable  
V.42, V.42 bis or MNP 25 only connection. If a V.42/V.42 bis/MNP 25 connection  
+ES=3, 2, 4  
cannot be established, the modem hangs up.  
Table 20 lists connection types corresponding to +ES settings.  
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Error Correction and Data Compression  
Table 20. Resulting +ES Connection Types  
+ES Settings (Answer Modem)  
+ES=3, 0, 2  
+ES Settings  
(Originate Modem)  
+ES=1, 0, 1  
(Buffer)  
+ES=4, 4, 6  
+ES=3, 2, 4  
(V.42 Reliable)  
(V.42 Auto-  
(MNP Reliable)  
reliable)  
+ES=1, 0, 1  
Buffer (normal) mode Modem hangs up Buffer (normal) mode Modem hangs up  
(Buffer)  
+ES=4, 4, 6  
Modem hangs up  
Buffer (normal) mode  
Modem hangs up  
MNP 25  
MNP 25  
MNP 25  
MNP 25  
MNP 25  
(MNP Reliable)  
+ES=3, 0, 2  
V.42/V.42 bis  
V.42/V.42 bis  
V.42/V.42 bis  
V.42/V.42 bis  
(V.42 Auto-reliable)  
+ES=3, 2, 4  
(V.42 Reliable)  
NOTES:  
MNP 5 requires the modem to be configured for %C1.  
V.42 bis requires the modem to be configured for H3.  
Refer to \Cn and %An commands for more information about auto-reliable mode.  
The list of commands needed to enter a specific error correction or data compression mode are as  
follows:  
V.42 bis with fallback to MNP5,  
&F +ES=3,0,2  
or +ES=3,0,2 H3 %C1  
MNP24 or V.42:  
V.42 bis with fallback to V.42/MNP24: &F +ES=3,2,4 %C0  
or +ES=3,2,4 %C0 H3  
-J1  
V.42 bis only:  
V.42 only:  
&F +ES=3,2,4 -J0  
or +ES=3,2,4 -J0 H3  
or +ES=3,2,4 -J0 H0  
&F +ES=3,2,4  
-J0 H0  
MNP5 with fallback to MNP24:  
MNP24 only:  
&F +ES=4,4,6  
or +ES=4,4,6 %C1  
or +ES=4,4,6 %C0  
&F +ES=4,4,6 %C0  
Table 21. V.44/V.42/V.42 bis and MNP Data Modem Command Descriptions  
Command Default  
Description  
Set Auto-Reliable Fallback Character: In auto-reliable mode (+ES=3,0,2) with auto-reliable fallback  
character enabled (\C2), receipt of the fallback character from the line during the V.42 detection phase  
causes the modem to switch to buffer (normal) mode. This allows a remote user with a non-V.42 modem  
to connect immediately with a V.42 modem. A space or carriage return is usually chosen for the fallback  
character.  
%An  
%Cn  
13  
n = 0127 (ASCII character)  
MNP 5 Data Compression Control: This command controls whether the data sent during the MNP  
frames is compressed using MNP Class 5 compression standard. MNP 5 data compression can improve  
throughput by as much as 150%.  
1
Range: 0, 1  
n = 0  
No compression  
n = 1*  
MNP Class 5 compression  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Error Correction and Data Compression  
Table 21. V.44/V.42/V.42 bis and MNP Data Modem Command Descriptions (Continued)  
Command Default  
Description  
MNP Block Size: This command specifies the maximum number of data bytes in an MNP data frame. A  
smaller frame size may improve throughput on high-impairment (noisy) telephone lines.  
Range: 03  
n = 0  
n = 1  
n = 2  
n = 3*  
Maximum 64 characters  
Maximum 128 characters  
Maximum 192 characters  
Maximum 256 characters  
\An  
\Bn  
3
Transmit Break: This command causes the modem to send a break (attention signal) to the remote for  
duration specified by n. nis specified in 100 ms units. When n = 0, the default break length is used.  
3
Range: 09  
Set Auto-Reliable Buffer (requires a license from Microcom*): In auto-reliable mode (+ES=3,0,2), this  
command determines the fallback method and enables data buffering. The settings for this command are  
used by the modem during the V.42 detection phase.  
Range: 02  
\Cn  
0
n = 0*  
n = 1  
n = 2  
Does not buffer data.  
Reserved.  
Does not buffer data. Switches to buffer (normal) mode upon receipt of auto-reliable  
fallback character and passes it to serial port. This feature allows non-V.42 modems to  
connect immediately to a V.42 modem without data loss.  
Set Modem Port Flow Control: In buffer (normal) mode (either +ES=1,0,1 or after fallback), this  
command enables modem-to-modem flow control using XOFF (13h) to stop and XON (11h) to start  
transmission between modems.  
\Gn  
0
0
n = 0, 1  
n = 0*  
n = 1  
Disables port flow control  
Sets port flow control to XON/XOFF  
bps Rate Adjust Control: If this command is enabled, the serial port speed automatically changes to the  
modem-connection speed. This forces the user to change the DTE-to-modem bps rate, if needed. If the  
command is disabled, the serial port speed is independent of the connection speed, which allows much  
greater throughput when using error correction and data compression.  
\Jn  
n = 0, 1  
n = 0*  
n = 1  
Turns off feature  
Turns on feature  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Error Correction and Data Compression  
Table 21. V.44/V.42/V.42 bis and MNP Data Modem Command Descriptions (Continued)  
Command Default  
Description  
Set break control: Defines what action the modem takes when a break (attention signal) is sent or  
received, as described below:  
where n =,  
In connect state, transmits break to remote (if in reliable mode):  
0, 2, 4  
Enters command mode, no break sent  
Destructive/expedited  
1
3
5
Nondestructive/expedited  
Nondestructive/nonexpedited  
\Kn  
5
In command state, transmits break to remote (if in reliable mode):  
0, 1  
2, 3  
4, 5  
Destructive/expedited  
Nondestructive/expedited  
Nondestructive/nonexpedited  
In connect state, receives break at modem port and sends to serial port:  
0, 1  
2, 3  
4, 5  
Destructive/expedited  
Nondestructive/expedited  
Nondestructive/nonexpedited  
Set Inactivity Timer: During a buffer (normal) or reliable connection, if no data is sent or received within  
the inactivity time period, the link is disconnected. The default, 0, disables this feature.  
\Tn  
\Xn  
0
0
Range: 090 Length in minutes  
n = 0*  
Disables inactivity timer  
Set XON/XOFF Pass-Through: If software flow control is enabled (\Q1), this command defines whether  
the XON (11h) and XOFF (13h) characters received from the DTE are sent to the remote modem. In  
addition, if the modem port flow control is enabled (\G1) in normal mode, the command specifies whether  
the XON and XOFF characters received from the remote modem are sent to the DTE. In both cases, flow  
control operation is not affected.  
Range: 0, 1  
n = 0*  
n = 1  
Processes flow control characters*  
Processes flow control characters and passes them through to the local or remote so they  
can process the characters.  
Set V.42 Detect Phase: In V.42 modes (+ES=3,0,2 and +ES=3,2,4), this command specifies whether the  
modem detects V.42, MNP, or no error-correcting protocols from the remote modem and changes to the  
appropriate mode. Otherwise, only V.42 is attempted.  
-Jn  
1
Range: 0, 1  
n = 0  
Disables the V.42 detect phase  
Enables the V.42 detect phase  
n = 1*  
V.42 bis Compression Control: This command specifies whether the data in the LAPM frames are  
compressed using V.42 bis data compression. This can improve throughput by as much as 400%.  
Compression can be negotiated to operate in one direction or both.  
Range: 03  
Hn  
On  
3
n = 0  
n = 1  
n = 2  
n = 3*  
Disables V.42 bis  
Enables V.42 bis only when transmitting data  
Enables V.42 bis only when receiving data  
Enables V.42 bis for both transmitting and receiving data  
V.42 bis String Length: This command specifies the maximum number of characters that can be  
compressed into one V.42 bis code word. The default value of 32 optimizes throughput for most file types.  
32  
Range: 6250 Number of characters  
n = 32*  
Usual number of characters  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Error Correction and Data Compression  
Table 21. V.44/V.42/V.42 bis and MNP Data Modem Command Descriptions (Continued)  
Command Default  
Description  
Data Compression Reporting: Controls whether the +DR:result code is transmitted from the DCE to  
DTE once a connection with has been made. If enabled the result code displayed shall represent the  
current negotiated DCE-DCE data compression type and is issued after the Error Control Report (+ER)  
and before the final result code CONNECT. +DR accepts one numeric parameter decimal value and the  
format is as follows:  
0
1
Disables Data compression reportingNo +DR result code transmitted  
Enables Data compression reporting+DR result code transmitted  
+DR=m  
0
Display messages when +DR = 1,  
+DR: NONE  
+DR: V42B  
Data compression not in use  
V.42 bis is in use in both directions  
V.42 bis is in use in receive direction only  
V.42 bis is in use in transmit direction only  
MNP5 in use  
+DR: V42B RD  
+DR: V42B TD  
+DR: MNP5  
Data Compression: This command sets multiple parameters for the control of data compression.  
m = <direction>, <compression negotiation>, <max dict>, <max string> Default: m = 3, 0, 2048, 6  
<direction> Specifies the direction of the data compression from the DTEs point of view.  
Range: <direction> = 03  
Default: <direction> = 3  
<direction> = 0  
<direction> = 1  
<direction> = 2  
<direction> = 3*  
Negotiated, no compression  
Transmit only  
Receive only  
Both directions, accept any direction  
<compression negotiation>Specifies whether the modem should stay connected or disconnect based  
on the desired result.  
+DS=m  
see m’  
Range: <compression negotiation> = 0, 1  
Default: <compression negotiation> = 0  
<compression negotiation> = 0* Do not disconnect  
<compression negotiation> = 1 Disconnect  
<max dictionary> Specifies the maximum number of dictionary entries that should be negotiated.  
Range: <max dictionary> = 512 to 65535  
Default: <max dictionary> = 2048  
<max string>  
Specifies the maximum string length to be negotiated.  
Range: <max string> = 6250  
Default: <max string> = 6  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Error Correction and Data Compression  
Table 21. V.44/V.42/V.42 bis and MNP Data Modem Command Descriptions (Continued)  
Command Default  
Description  
V.44 Data Compression: This command controls the V.44 data compression function if provided in the  
DCE. It accepts the following sub parameters:  
m=[<direction>[,<compression_negotiation>[,<capability>[,<max_codewords_tx>[,<max_codewords_rx>  
[,<max_string_tx>[,<max_string_rx>[,<max_history_tx>[,<max_history_rx>]]]]]]]]]  
<direction> specifies the desired direction(s) of operation of the data compression function.  
0
1
2
3
Negotiatedno compression  
Transmit only  
Receive only  
Both directions, accept any direction  
<compression_negotiation> specifies whether or not the DCE should continue to operate if the desired  
result is not obtained.  
0
Do not disconnect if Rec. V.44 is not negotiated by the remote DCE as specified in  
<direction>. Always set to 0.  
<capability> specifies the use of stream method, packet method, multi-packet method.  
3, 0, 0,  
471,  
942,  
0
1
2
Stream method  
Packet method  
+DS44=m  
140,  
Multi-packet method  
140,  
1884,  
3768  
<max_codewords_tx> specifies the maximum number of codewords which should be negotiated in the  
transmit direction.  
256 to 65536  
<max_codewords_rx> specifies the maximum number of codewords which should be negotiated in the  
receive direction.  
256 to 65536  
<max_string_tx> specifies the maximum string length to be negotiated in the transmit direction.  
32 to 255  
<max_string_rx> specifies the maximum string length to be negotiated in the receive direction.  
32 to 255  
<max_history_tx> specifies the maximum size of the history buffer to be negotiated in the transmit  
direction.  
512  
<max_history_rx> specifies the maximum size of the history buffer to be negotiated in the receive  
direction.  
512  
32-bit Frame Check Sequence: Controls the use of 32-bit frame check sequence option in V.42.  
0
1
2
Use 16-bit FCS  
+EFCS=m  
0
Use 32-bit FCS if available in remote DCE; otherwise use 16-bit FCS  
Use 32-bit FCS if available in remote DCE; otherwise disconnect  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Error Correction and Data Compression  
Table 21. V.44/V.42/V.42 bis and MNP Data Modem Command Descriptions (Continued)  
Command Default  
Description  
Error Control Reporting: Controls whether the +ER:result code is transmitted from the DCE to the  
DTE once a connection has been made. If enabled the result code displayed shall represent the current  
negotiated DCE-DCE error control type and is issued after the Modulation Report (+MCR and +MRR) and  
before the final result code Data Compression Report (+DR:). +ER accepts one numeric parameter  
decimal value and the format is as follows:  
0
1
Disables error control reporting (no +ER intermediate result code transmitted)  
Enables error control reporting (+ER intermediate result code transmitted)  
Display messages when +ER = 1,  
+ER=m  
0
+ER: LAPM  
V42 LAPM protocol in use  
+ER: MNP 2  
MNP 2 protocol in use  
+ER: MNP 2 4  
+ER: MNP 3  
MNP 2 and 4 protocol in use  
MNP 3 protocol in use  
+ER: MNP 3 4  
Example if +ER = 1  
+ER: LAPM  
MNP 3 and 4 protocol in use  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Error Correction and Data Compression  
Table 21. V.44/V.42/V.42 bis and MNP Data Modem Command Descriptions (Continued)  
Command Default  
Description  
Error Control Selection: The +ES=m command controls the operation of the V.42 error detection and  
correction protocol in the DCE. Once a connection has been established between the DCE and DTE, the  
<orig_rqst> subparameter can put the interface into synchronous access mode. In the default settings,  
synchronous access mode is disabled. To change modes, send another +ES command.  
+ES=1,0,1  
+ES=4,4,6  
+ES=3,0,2*  
+ES=3,2,4  
+ES=2,3,5  
+ES=6, ,8  
Buffered mode  
MNP reliable mode  
V.42 autoreliable mode  
V.42 reliable mode  
LAPM reliable mode  
Synchronous access mode  
m = <orig_rqst>, <orig_fbk>, <ans_fbk>  
Defaults: m = 3, 0, 2  
<orig_rqst> Specifies the initial requested mode of operation when the DCE is the originator. If  
<orig_rqst>=6, the modem ignores the <orig_fbk> setting.  
Range: 14, 6  
0
1
2
Reserved.  
Initiate call with buffered mode only.  
Initiate V.42 without detection phase. If V.80 mode is in use, this is a request to disable V.42  
detection phase.  
3*  
4
Initiate V.42 with detection phase.  
Initiate alternate protocol.  
6
Initiate synchronous access mode when connection is completed and when in data state.  
<orig_fbk> Specifies the acceptable fallback mode of operation when the DCE is the originator. This  
setting is ignored if <orig_rqst>=6.  
Range: 02, 4  
+ES=m  
see m’  
0*  
Error control optional (either LAPM or alternative acceptable). If error control is not  
established, maintain the DTE-DCE data rate and use the V.14 buffered mode with flow  
control during non-error control operation.  
1
2
Error control optional (either LAPM or alternative acceptable). If error control is not  
established, change the DTE-DCE data rate to match the line rate and use direct mode.  
Error control required (either LAPM or alternative acceptable). If error control is not  
established, disconnect.  
3
4
Reserved.  
Error control required (only alternative protocol acceptable). If error control is not established,  
disconnect.  
<ans_fbk> Specifies the acceptable fallback mode of operation when the DCE is the answerer.  
Range: 1, 2, 46, 8  
0
Direct mode.  
1
Error control disabled, use buffered mode.  
2*  
Error control optional (either LAPM or alternative acceptable). If error control is not  
established, maintain the DTE-DCE data rate and use local buffering and flow control during  
non-error control operation.  
3
4
Reserved.  
Error control is required (either LAPM or alternative is acceptable). If error control is not  
established, disconnect.  
5
6
Error control required (only LAPM acceptable). If error control is not established, disconnect.  
Error control required (only the alternative protocol is acceptable). If error control is not  
established, disconnect.  
8
Initiate synchronous access mode when the connection is complete and data state is entered.  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Fax Class 1 AT Commands  
Fax Class 1 AT Commands  
5
The 536EX chipsets implement the EIA-578 data/fax Class 1 AT command set standard. This AT  
command set allows a DTE (with Class 1 communication software) and a 536EX-based modem to  
communicate with Group 3 fax machines. In addition, these chipsets provide fax identity and test  
commands. Fax identity commands are described in Table 22; all other fax AT commands are  
provided in Table 24 on page 67.  
5.1  
Fax Identity Commands  
The fax identity commands are AT+FMFR?, AT+FMDL?, AT+FMI, AT+FMM, AT+FMR, and  
AT+FREV?. These commands respond back with modem manufacturer, product model, and  
product revision information.  
Table 22. Fax Identity Command Descriptions  
Command  
Default  
none  
Description  
Identifies Modem Manufacturer: This command causes the DCE to send a message to the DTE  
indicating the DCE manufacturer. This command is identical to ATI2 and AT+GMI.  
AT+FMFR?  
Intel Corporation  
+FMFR?/+FMI  
OK  
Identifies Product Model: This command causes the DCE to report the modem chipset name.  
This command is identical to ATI1 and AT+GMM.  
AT+FMDL?  
Intel 536EP V.92 Modem  
+FMDL?/+FMM  
+FREV?/+FMR  
none  
none  
OK  
Identifies Product Version Number: This command causes the DCE to report the modem  
chipset revision level. This command is identical to ATI4 and AT+GMR.  
AT+FREV?  
536EP Release 4.28 - Dec 10 2001  
OK  
5.2  
Fax Class 1 Commands  
The fax Class 1 AT commands are divided into three types: class selection and capabilities, data  
stream transfers, and silence-time timers. All fax mode commands, except the silence-time timers,  
must be the last command on the command line.  
Each command may be used as follows:  
+F<command>?  
Reads current setting  
+F<command> = ?  
Reads permissible settings  
+F<command> = <parameter> Sets parameters  
Note: To originate a call, answer, and hang up, use the ATD, ATA, and ATHn commands, respectively.  
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Fax Class 1 AT Commands  
The fax AT+FCLASS command is used for changing between fax classes, determining the current  
class selection, and determining the supported fax classes. Both data/fax Class 0 (data modem  
mode) and Class 1 (fax modem mode) are implemented by the modem. In Class 0, the DTE-to-  
modem data rate can be set from 300 bps to 115,200 bps. In Class 1, it is recommended that the  
DTE-to-modem data rate is set to 19,200 bps.  
The silence-time timers consist of AT+FTS=<TIME> and AT+FRS=<TIME>. Silence time is  
defined as the length of time when the modem neither receives nor transmits energy (that is,  
modem transmit carrier) on the telephone line.  
The modem exchanges streams of data with the DTE while executing the data transfer commands  
AT+FTM=<mod>, AT+FTH=<mod>, AT+FRM=<mod>, and AT+FRH=<mod>. The values  
supported for <mod> are provided in Table 23.  
During data transfer, an ASCII <DLE>character ($10h) is used as a special character to shield  
other special characters.  
Special characters in the data stream are used in the following way:  
any data ... <DLE><ETX>  
any data ... <DLE><DLE>  
any data ... <DLE>  
end of data stream  
single 10h<DLE> in data stream  
<not DLE or ETX>  
delete both <DLE> and next character  
When the DTE transfers data to the modem, the DTE must insert a <DLE>for each <DLE>in the  
original data stream. In addition, when data is no longer available, the DTE must add the stream  
terminator <DLE><ETX>to the end of the data stream. The modem buffers up to one thousand  
bytes of fax data before sending it to the remote modem (AT+FTM command). If the modem  
detects the two terminating characters <DLE><ETX>within the data stream, it transmits the data  
immediately to the remote modem without waiting for the buffer to fill up.  
Table 23. <mod> Selection Table  
Value  
Modulation  
Speed (bps)  
3
V.21 ch 2  
V.27 ter  
V.27 ter  
V.29  
300  
24  
2400  
4800  
7200  
7200  
7200  
9600  
9600  
9600  
12,000  
12,000  
14,400  
14,400  
48  
72  
73  
V.17  
74  
V.17 with short train  
V.29  
96  
97  
V.17  
98  
V.17 with short train  
V.17  
121  
122  
145  
146  
V.17 with short train  
V.17  
V.17 with short train  
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Fax Class 1 AT Commands  
When the modem transfers data to the DTE, the DTE must filter the data stream by removing all  
character pairs beginning with <DLE>. The DTE also must recognize <DLE><ETX>as the stream  
terminator. Upon detecting <DLE><DLE>, the DTE must reinsert a single <DLE>in its place. The  
modem buffers up to 512 bytes of fax data received from the remote modem if the DTE cannot  
read the data immediately (AT+FRM command).  
For the AT+FTH and AT+FRH commands, data is sent and received using HDLC formatting. The  
format for HDLC framing is provided below. When sending the HDLC data, the modem  
automatically generates the flags and the frame checking sequence (Frame Check Sum). All the  
other fields are transmitted to or received from the DTE (that is, these fields are under the control  
of the DTE).  
Figure 8. T.30 HDLC Frame Format  
Frame  
Facsimile  
Control  
Field  
Facsimile  
Information  
Field  
Checking  
Address  
Field  
Control  
Field  
Flag  
Flag  
Flag  
Sequence  
(FCS)  
After receiving a frame correctly using the AT+FRH command (FCS is OK), the DCE returns an  
OKmessage to the DTE. If the frame is received in error (FCS is not OK, carrier is lost, or data is  
lost due to data overflow), the DCE returns an ERRORmessage to the DTE; the DTE should then  
discard the frame.  
Note: If the telephone line is on-hook, the modem responds back to the DTE with an ERRORmessage  
whenever any of the fax AT commands, except the +FCLASS command, are sent to the modem.  
Figure 9. CLASS 1 DTE-Generated HDLC Frame Information (AT+FTH=<mod>)  
Facsimile  
Control  
Field  
Facsimile  
Information  
Field  
Address  
Field  
Control  
Field  
Figure 10. CLASS 1 DTE Reception of HDLC Frame Information (AT+FRH=<mod>)  
Frame  
Checking  
Sequence  
(FCS)  
Facsimile  
Control  
Field  
Facsimile  
Information  
Field  
Address  
Field  
Control  
Field  
Like the data modem mode, the DTE needs to issue an ATD string or ATA command to the modem  
to originate or answer a fax call. Unlike the data modem mode, auto-answering is not supported by  
the modem while in fax mode. It is recommended that S-register S0 be set to 0(that is, use ATA)  
whenever the modem is expected to receive a fax call.  
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Fax Class 1 AT Commands  
The ATDT <telephone number> command string causes the modem to originate a fax call. After  
dialing the telephone number, the modem sends out a calling tone (1100 Hz), recognizes the remote  
fax modem answer tone, and looks for the remote fax HDLC flags at 300 bps. If the HDLC flags  
are detected, the modem sends the DTE a CONNECTmessage followed by the Class 1 HDLC  
frame information. If the HDLC flags are not detected within the time limit defined by S-register  
S7, the modem sends a NO CARRIERmessage to the DTE and then hangs up the line. If the  
modem hangs up the line while processing the ATD command (that is, while the modem is on-  
hook), the modem responds back with an ERRORmessage whenever the DTE issues one of the  
data stream AT commands.  
The ATA command causes the modem to answer a fax call. After going off-hook, the modem sends  
the answer tone followed by HDLC flags. The modem then sends a CONNECTmessage to the  
DTE and waits to receive the HDLC frame information from the DTE. In general, the ATA  
command performs three functions:  
1. It places the modem off-hook.  
2. It causes the modem to transmit the answer tone.  
3. It causes the modem to act as if it received an AT+FTH=3 command from the DTE.  
The following data mode and voice mode AT commands are supported in fax mode:  
Data: All  
Voice: +FCLASS, +VDR, +VNH, +VIP, and + VCID  
Table 24. Fax Mode Command Descriptions  
Command Default  
Description  
Fax Mode Selection: This command is used to select a fax class, indicate current fax  
class mode setting, and indicate supported fax classes. All fax mode commands,  
except for +FCLASS, are valid only in fax mode.  
+FCLASS?  
Indicates current fax class selection  
+FCLASS = ? Indicates supported fax classes  
+FCLASS = n Configures DCE for selected fax class. The modem  
responds back with an OKmessage at the same  
+FCLASS  
0
=1  
DTE-to-modem data rate used to issue this command  
Range: 0, 1, 8  
n = 0*  
n = 1  
n = 8  
Configures DCE for data modem operation  
Configures DCE for fax Class 1 modem operation  
Configures DCE for IS-101 voice mode  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Fax Class 1 AT Commands  
Table 24. Fax Mode Command Descriptions (Continued)  
Command Default  
Description  
Receive HDLC Data: The +FRH=<mod> command causes the modem to receive  
HDLC-framed data using the modulation mode selected in <mod>. The modem then  
delivers the next-received frame to the DTE.  
If the modem detects the selected carrier signal with an HDLC flag, the modem sends  
a CONNECTresult code to the DTE. If the modem detects a different signal, the  
modem sends the +FCERROR(fax connect error) result code to the DTE and returns  
to command mode. Upon loss of carrier, the modem returns to command mode and  
sends a NO CARRIERresult code to the DTE.  
After receiving the HDLC flags, the modem strips away the flags and buffers the  
received frames. The modem then transfers the received data to the DTE, starting with  
the first non-flag byte and continuing through the last FCS byte. The DTE should  
ignore the value of the FCS bytes. The modem also performs HDLC zero-bit deletion  
and error checking.  
After the FCS bytes are transferred, the modem marks the end of the frame with  
<DLE><ETX> and reports the status of the frame reception to the DTE. If the frame  
was received correctly (FCS is correct), the modem returns a OKresult code. If the  
frame was received in error (FCS is not correct, carrier lost, or data lost due to data  
overflow), the DCE returns an ERRORresult code. The DTE should then discard this  
frame.  
+FRH=m  
none  
After sending the status result code, the modem is ready to accept new commands  
from the DTE.  
The modem obeys the configured flow control from the DTE. If the DTE sends any  
character to the modem other than DC1 or DC3 while the modem is in this mode, the  
modem enters command mode and return an OKresult code.  
After sending the result code indicating that frame reception is complete, the modem  
continues to receive and buffer the data in the selected mode. If the DTE issues  
another +FRH=<mod> command, the modem returns another CONNECTresult  
code and continues with HDLC reception. If the DTE issues any command that  
changes modulation, the DCE stops the receive process; the DCE then discards any  
buffered data and processes the command.  
Range: <mod> = 3  
Refer to Table 23 on page 65.  
Receive Data: The +FRM=<mod> command causes the modem to enter receive  
mode using the modulation scheme specified in <mod>. <mod> may have the values  
shown in Table 23 on page 65.  
When the selected carrier is detected, the modem sends a CONNECTresult to the  
DTE. If a different signal is detected, the modem sends a +FCERROR(connect error)  
result code to the DTE and returns to command mode.  
After receiving the selected carrier, the modem transfers all received data patterns to  
the DTE as consecutive start-stop framed bytes, including leading marking conditions  
or flags. The modem marks the end of the data stream with <DLE><ETX>.  
+FRM=m  
none  
Upon loss of carrier, the modem returns to command state and sends a NO  
CARRIERresult code to the DTE.  
NOTE: If the modem is on-hook, then the modem always returns an ERROR’  
message to the DTE after receiving the +FRM=<mod> command.  
Range: <mod> = 24, 48, 72, 73, 74, 96, 97, 98, 121, 122, 145, 146  
Refer to Table 23 on page 65.  
Wait for Silence: The +FRS=<TIME> command causes the modem to send an OK’  
result code to the DTE when silence has been detected on the line for the amount of  
time specified. The value <TIME> is in 10 ms intervals. The command terminates  
when the required amount of silence has been detected on the line or the DTE sends  
the modem another character that is discarded. In either event, the DTE returns the  
OKresult code.  
+FRS=m  
none  
Range: <TIME> = 1255 (10 ms)  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Fax Class 1 AT Commands  
Table 24. Fax Mode Command Descriptions (Continued)  
Command Default  
Description  
Transmit HDLC Data: The +FTH=<mod> command causes the modem to transmit  
data framed in HDLC protocol using the modulation mode selected. <mod> may have  
the values shown in Table 23 on page 65.  
After receiving the +FTH command, the modem sends a CONNECTresult code to  
the DTE. The modem then transmits signal converter training (if required) followed by  
flags until the first byte of data is sent by the DTE. The modem terminates the +FTH  
command upon detecting <DLE><ETX>characters in the data stream.  
When the buffer is empty, the modem computes and appends the FCS (Frame Check  
Sequence) and a closing flag to the frame. The modem ensures that the minimum  
number of flags required by T.30 are sent before the data from the DTE begins to be  
transmitted.  
The modem checks the final frame bit in the control field of each frame; this is the fifth-  
received bit of the second byte of each frame. If the final frame bit is a 1, the modem  
ceases transmission after the frame is sent, returns to command state, and sends the  
OKresult code to the DTE. If the final frame bit is a 0, the modem sends another  
CONNECTresult code to the DTE after the current frame is sent. The modem  
continues to transmit flags until the DTE takes one of the following actions:  
+FTH=m  
none  
The DTE sends additional data. The modem then transmits another frame.  
The DTE sends only <DLE><ETX>(a null frame). The modem then turns off the  
transmit carrier and send the OKresult code to the DTE.  
If the DTE transmits no additional data within 5 seconds from when the modem  
reported the CONNECTresult code, the modem turns off the transmit carrier  
mode, returns to command mode, and sends the ERRORresult code to the DTE.  
In HDLC transmit mode, the modem performs HDLC transparency functions, FCS  
generation, and buffers the transmit data. The modem uses the configured method of  
flow control to pause the DTE as necessary.  
NOTE: If the modem is on-hook, it always returns an ERRORmessage to the DTE  
after receiving the +FTH=<mod> command.  
Range: <mod> = 3  
Refer to Table 23 on page 65.  
Transmit Data: The +FTM = <mod> command causes the modem to transmit data  
using the modulation selected in <mod>.  
The modem returns a CONNECTresult code and transmits the proper training  
sequence in the selected mode, followed by constant 1bits until data is received from  
the DTE. The modem terminates this command upon detecting <DLE><ETX>  
characters in the data stream.  
If the modems transmit buffer empties and the last transmitted character is an ASCII  
NULL (00), the modem continues to transmit NULLs until the DTE sends more data or  
5 seconds have elapsed. After 5 seconds have elapsed with an empty transmit buffer,  
the DCE turns off the transmit carrier, returns to command state, and returns an  
ERRORresult code to the modem.  
+FTM=m  
none  
NOTE: Hex $00 replication does not provide the required timing needed for  
generating the TCF frame (1.5 seconds of 0s).  
If the modems transmit buffer empties and the last transmitted character was not a  
NULL, the modem turns off the transmit carrier, returns to command state, and sends  
the OKresult code to the DTE.  
NOTE: If the modem is on-hook, the modem always returns an ERRORmessage to  
the DTE after receiving the +FTM = <mod> command.  
Range: <mod> = 24, 48, 72, 73, 74, 96, 97, 98, 121, 122, 145, 146  
Refer to Table 23 on page 65.  
Stop Transmission and Pause: The +FTS=<TIME> command causes the modem to  
stop all transmissions. The modem waits for the specified amount of time, then sends  
an OKresult code to the DTE. The value <TIME> is in 10 ms intervals.  
+FTS=m  
none  
Range: <TIME> = 0255 (in 10 ms intervals)  
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
IS-101 Voice Mode AT Commands 6  
The 536EX chipsets implement a voice mode AT command set that allows a DTE to record and  
play back voice messages. This product is compatible with the EIA/TIA IS-101 voice command  
set. This section lists supported commands and a detailed description of each command (see  
Table 25 on page 71). When multiple commands are placed on a line, a semicolon (;) must be  
placed after each voice (and fax) command.  
Note: To originate a call, to answer, and to hang up, use the ATD, AT+VLS0, and AT+VLS=0  
commands, respectively.  
Each command may be used as follows:  
+V<command>?  
Read current setting  
+V<command> = ?  
Read permissible settings  
+V<command> = <parameter> Set parameter  
For example, AT+FCLASS? determines whether the modem is configured for data (or fax) mode  
or voice mode. AT+FCLASS=? determines which data/fax/voice modes are supported by the  
modem. AT+FCLASS=m switches between voice mode and data mode.  
The modem exchanges streams of data with the DTE while executing the commands for voice  
playback (AT+VTX) and record (AT+VRX) and while in voice command mode (with either the  
modem being off-hook or using the local phoneAT+VLS=m). In these modes, the DCE searches  
for DTMF, calling tone, and dial tones and reports them to the DTE whenever they are detected.  
Detection information and data stream terminators are passed between the DTE and DCE by first  
sending an ASCII <DLE>character ($10h) followed by a special character. Special characters in  
the data stream are used as follows:  
any data ... <DLE><ETX>  
end of data stream  
any data ... <DLE><DLE>  
single 10h<DLE> in data stream  
X is a special character,  
any data ... <DLE><X>  
delete both <DLE> and X from  
the data stream  
When the DTE transfers data to the modem during playback mode (AT+VTX command), the DTE  
must insert a <DLE>for each <DLE>in the original data stream. When data is no longer available,  
the DTE must add the stream terminator <DLE><ETX>to the end of the data stream. If the modem  
detects the two terminating characters <DLE><ETX>within the data stream, it transmits the data  
immediately to the remote modem without waiting for the buffer to fill up. To abort playback mode  
without waiting for the modem to empty the internal modem buffer, send  
<DLE><CAN><DLE><ETX>. Immediately aborting the playback mode eliminates long delays  
between receiving a DTMF tone or keyboard abort and starting a new function such as playing  
back or recording a new message.  
When the modem transfers data to the DTE during record mode (AT+VRX command), the DTE  
must filter the data stream by removing all character pairs beginning with <DLE>. The DTE also  
must recognize <DLE><ETX>as the stream terminator. Upon detecting <DLE><DLE>, the DTE  
must reinsert a single <DLE>in its place. The modem buffers up to 512 bytes of voice data  
received from the SAFE analog-to-digital converters if the DTE cannot read the data immediately.  
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IS-101 Voice Mode AT Commands  
6.1  
6.2  
DTMF Detection Reporting  
DTMF detection information is reported by the modem to the DTE by a <DLE> shielded command  
as outlined in Section 6.5 of the ITU V.253 specification. When the DTMF burst is detected in  
Voice mode, the modem sends to the DTE a <DLE></> followed by a sequence of <DLE><-> is  
inserted to indicate the end of the determination interval.  
For example, a single 280ms burst of DTMF 5 would report:  
<DLE></><DLE><5><DLE><5><DLE><5><DLE><5><DLE><->  
Relay Control  
To originate a call (that is, to originate call forwarding or auto-dialing) and to generate tones, use  
the dialing command:  
ATDT <telephone number>  
If the modem was not already off-hook, then this command automatically configures the value for  
AT+VLS=m to m = 1 or m = 5 depending on the value for Mn.  
To answer a call, use the AT+VLS=m command. Unlike data mode, the modem (when configured  
for voice mode) does not automatically answer an incoming call (that is, the modem ignores the  
contents of S-register S0).  
Remote playback/record takes place whenever the modem is off-hook (OHREL* is activated). For  
local playback/record, the modem is on-hook, and the user uses a local telephone or handset. The  
LPHREL* relay driver may be used to control the local telephone or handset when implementing  
local playback/record mode (AT+VLS=m). Additionally, voice messages may be played through  
the modem/computer speaker. The 536EX chipsets also provide a microphone interface that can be  
used for local recording.  
In voice mode, all voice AT commands can be issued by the DTE at any valid speed between 300  
bps to 115,200 bps. Typically, the DTE-to-modem data rate is set for 19,200 bps, which is the  
recommended data rate for Class 1 fax mode. The DTE-to-modem data rate may need to be set to  
115,200 bps in certain instances, such as during playback or during record mode for a CL1  
compression scheme.  
The following data and fax AT commands are supported in voice mode:  
Data:  
All except ATA, ATIn  
Fax:  
+FCLASS  
Table 25. Voice Mode Command Descriptions  
Command  
Default  
Description  
Voice Mode Selection: This command enables or disables voice mode. All voice mode commands  
(except for +FCLASS=m) are valid only in voice mode.  
+FCLASS  
=8  
0*  
1
Data mode  
0
Class 1 fax mode  
Voice mode enabled  
8
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
Table 25. Voice Mode Command Descriptions (Continued)  
Command  
Default  
Description  
Flow Control Select: This command allows the DTE to identify and select the types of flow control  
used. DCEs using the IS-101 standard must support in-band XON/XOFF flow control. XON is the  
ASCII <DCI>character (11h); XOFF is the ASCII <DC3>character (13h). The DCE may provide ITU-Ts  
V.24 CTS (circuit 106) and RTS (circuit 133) for flow control.  
+FLO=m  
1
0
Disables XON/XOFF and CTS/RTS flow control  
Enables XON/XOFF flow control in either direction  
1*  
2
The DTE uses ITU-Ts RTS to control flow to the modem; the modem uses ITU-T CTS to  
control flow to the DTE.  
Buffer Threshold Setting: This command specifies the flow control assert and deassert points inside  
the DCEs internal transmit buffer. The internal buffer is 512 bytes. The +VBT=m parameters are fixed  
in firmware and cannot be changed.  
m = <deassert>, <assert>  
Defaults: <deassert> = 192, <assert> = 320  
<assert>: This parameter stops data transfer from the DTE when the number of bytes in the buffer  
reaches the lower number of the range specified by the <assert> parameter. So that no data is lost  
before the modem stops the flow of data, the <assert> parameter allows more data to enter the buffer  
until it reaches the larger number in its range.  
+VBT=m  
see m’  
Range: <assert> = 192  
<deassert>: This parameter starts data transfer from the DTE after the number of bytes in the transmit  
buffer falls below the <deassert> value.  
Range: <deassert> = 320  
Caller ID Selection: This command controls the reporting and presentation of data in the ICLID  
(Incoming Call Line ID) data format used by the Caller ID services in the United States and Canada. At  
a minimum, the data sent to the DCE includes the date, time, and the callers telephone number. Caller  
ID information is sent to the DTE during the first and second ring signals when the modem is in voice,  
data, or fax mode.  
0*  
1
Disables Caller ID  
+VCID=m  
0
Enables Caller ID with formatted presentation to the DTE. The modem presents the data  
items in a <Tag><Value> pair format. The expected pairs are data, time, caller code  
(phone number), and name.  
2
Enables Caller ID with unformatted presentation to the DTE. The modem presents the  
entire packet of information, excluding the leading Us, in ASCII-printable hex numbers.  
NOTE: If S0=1 (auto-answer mode) and Caller ID is enabled in data modem mode, then the modem  
answers only after the second ring signal.  
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
Table 25. Voice Mode Command Descriptions (Continued)  
Command  
Default  
Description  
Distinctive Ring Selection: This command contains two parameters. The first selects whether the  
modem reports distinctive ring cadence information. The second parameter controls the timing of the  
RING event code report.  
m=<enable>, <report>  
Defaults = 0, 0  
<enable> Ring Reporting: The DCE reports the length of the ring period.  
Range: <enable> = 0255 (enables/disables distinctive ring reporting in the form DROF=<number in  
units of 0.1 seconds><CR><LF>)  
<report> Time Ring Reporting: The DCE reports the silence periods length. The DCE may produce  
a RING event code after the DRON message if enabled by the <report> parameter. The <report>  
parameter should be set to a value larger than the expected off-times within a single pattern so the  
RING even reports are issued only during the off-times between the complex patterns.  
+VDR=m  
see m’  
Range: <report> = 0255 (reporting type in the form DROF=<number in  
units of 0.1 seconds>)  
<enable> <report>  
Function  
0
1
Distinctive ring disabled  
The modem reports DROF and DRON messages but does not report RING  
messages  
0
1
non-0 The modem reports DROF, DRON and RING messages  
Reserved  
2255  
Regardless of its setting, the +VDR command can be disabled by the +VEM command.  
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
Table 25. Voice Mode Command Descriptions (Continued)  
Command  
Default  
Description  
Event Reporting and Masking: This command selects which detection events are supported in voice  
mode. Each event is represented by a single bit of a four-digit hex number (see the following table).  
Setting an event number bit to 0 means that event is not reported. Setting a bit to 1 indicates that a  
detected event is reported. While the event settings affect all modes (that is, playback, record, and  
command modes), not just voice command mode, the mask can be changed each time the mode is  
changed. Not all events are supported in each mode. See the following table for supported events.  
This modem supports more features than an IS-101 Class C-compliant modem. (Class C is the highest  
IS-101 compliant modem, and Class A is the lowest.) See the following examples for more information.  
m = <mask>  
Defaults = C, BB860980, BFE63883, BB863EE0  
Event  
Number  
(Bit Number)  
Hex Digit  
Location  
Event Description  
Caller ID report  
DCE Voice Mode(s)  
1
0
1
Command  
Reserved  
2
Distinctive ringing  
RING  
DTMF received  
Receive buffer overrun  
Fax calling (for example, 1100 Hz)  
Data calling (for example, 1300 Hz)  
Local phone on/off hook  
Presumed hang-up (SILENCE) time-out  
Presumed end of message (QUIET) time-  
out  
All  
All  
All  
Receive  
All  
All  
All  
Receive  
3 *  
4 *  
5 *  
6 *  
7
2
3
8
9 *  
10 *  
Receive and command  
11  
12  
13  
14  
15  
16  
17  
18 *  
19 *  
20 *  
21  
22  
23*  
24  
25 *  
26  
27  
Reserved  
Reserved  
Loop current interruption  
Loop current polarity reversal  
Reserved  
Reserved  
Reserved  
Ringback/remote ring  
BUSY reorder/fast busy  
DIALTONE  
4
5
6
7
8
+VEM=m  
see m’  
All  
All  
All  
Receive and Command  
Receive and Command  
Reserved  
Reserved  
Transmit buffer under-run  
Extension phone on/off hook  
Fax or data answer (for example, 2100 Hz) Command  
Data answer (for example, 2225 Hz)  
Reserved  
Reserved  
Transmit  
All  
Command  
28  
29  
Reserved  
30  
Reserved  
31  
Reserved  
32  
Reserved  
33  
Reserved  
34  
Reserved  
35  
Reserved  
NOTES:  
Items marked with an asterisk (*) meet IS-101 Class C specifications.  
All: Playback, record, and command modes.  
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
Table 25. Voice Mode Command Descriptions (Continued)  
Command  
Default  
Description  
Event Reporting and Masking: (cont.)  
Example 1. Viewing Supported Events:  
To determine what events are supported by the modem, send AT+VEM=?.  
AT+VEM=?  
CFeature Class  
DB860980 Playback mode events  
OFEE0883 Record mode events  
BB863EE0 Command mode events  
OK  
Example 2. Setting the Event Mask:  
To set the event mask, issue AT+VEM=m, where mis eight hex digits. This command is issued only in  
command mode and is followed when changing between voice modes. That is, the modem uses the  
event mask previously set by the +VEM=m command when entering playback or record mode. The  
modem ignores any event bit set when that feature is not supported in that voice mode.  
+VEM=m  
(cont.)  
see m’  
AT+VEM=BB863EE0  
Example 3. Reading the Event Mask Settings:  
To read the settings for each event, type:  
AT+VEM?  
BB863EE0  
OK  
Example 4. Understanding the +VEM Hexadecimal Code:  
The following illustration shows how the hexadecimal eight-digit code (BB863EE0) is derived from the  
bit setting for each event:  
HEX DIGIT LOCATION: 1 2 3 4 5 6 7 8  
EIGHT-DIGIT HEX CODE:B B 8 6 3 E E 0  
The following example shows how to read the string.  
EX VALUE  
3
B
B
6
E
8
0
E
BIT VALUE  
EVENT  
1 0 1 1 1 0 1 1  
1 0 0 0  
0 1 1 0  
0 0 11  
1 1 1 0  
0 0 0 0  
1 1 1 0  
20 21 22 23  
0 1 2 3  
4 5 6 7  
8 9 10 11  
12 13 14 15  
16 17 18 19  
24 25 26 27  
28 29 30 31  
HEX DIGIT  
LOCATION  
7
1
2
6
3
5
8
4
Speakerphone Microphone Gain: This command sets the speakerphones microphone gain.  
Range: 121131  
+VGM=m  
128  
128*  
Nominal value  
Receive Gain Selection: This command sets the recording level for the modems voice mode. A  
different recording level may be needed for each type of recording device. This includes telephone  
line, local handset, local telephone, or microphone.  
+VGR=m  
128  
128  
Range: 121131  
128*  
Nominal recording level  
Speakerphone Speaker Gain: This command sets the speakerphones speaker gain.  
Range: 121131  
+VGS=m  
128*  
121  
131  
Gain smaller than normal  
Gain larger than normal  
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
Table 25. Voice Mode Command Descriptions (Continued)  
Command  
Default  
Description  
Volume Selection: This command sets the volume level for the modems playback voice mode. A  
different playback level may be needed for each type of playback device (telephone line, local handset,  
local telephone, or speaker).  
+VGT=m  
128  
Range: 121131  
128*  
Nominal transmit level  
Initialize Parameter: This command causes the modem to initialize all voice parameters to the factory  
default values. This command does not change relay or speaker setup (that is, if the modem is off-  
hook, then the modem remains off hook after processing this command).  
+VIP  
none  
DTE/DCE Inactivity Timer: This command sets the length of time the modem can be inactive in voice  
mode before the modem resets its relays +VLS=0 and changes to data mode (FCLASS=0) with  
autobauding. The purpose of this timer is to ensure that the DTE does not leave the DCE in a mode  
that cannot be accessed by voice-unaware software. This timer is supported in playback, record and  
voice command mode. Sending any data (such as a <DLE><NUL>string) to the modem re-initializes  
this timer.  
+VIT=m  
0
Range: 0255 (units of 1.0 second)  
m = 0*  
Disables inactivity timer  
Inactivity timer active  
m 0  
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
Table 25. Voice Mode Command Descriptions (Continued)  
Command  
Default  
Description  
Relay/Playback Control: This command controls the four µP relay drivers and controls hardware  
paths for voice playback/record transmit and receive.  
Preassigned Voice I/O Labels  
<label>  
Primitive Code  
Description  
0
None  
DCE on hook. Local phone connected to Telco.  
DCE off hook. DCE connected to Telco. Local phone provided with  
power to detect the hook condition.  
DCE on hook. Local phone connected to DCE.  
DCE off hook. Local phone connected to Telco. DCE connected to  
Telco. (Not implemented. Return error.)  
1
2
3
T
L
LT  
Internal speaker connected to DCE. DCE on-hook. Local phone  
connected to Telco.  
Internal speaker connected to Telco. DCE off-hook. DCE  
connected to Telco. Local phone provided with power to detect  
hook condition.  
4
5
6
7
8
9
S
ST  
Internal microphone connected to DCE. DCE on hook. Local  
phone connected to Telco.  
M
Internal microphone and internal speaker connected to Telco.  
Squelching active. DCE off hook. DCE connected to Telco. Local  
phone provided with power to detect hook condition.  
External speaker connected to DCE. DCE on-hook. Local phone  
connected to Telco. (Implemented as 4. Speaker jack determines.)  
External speaker connected to Telco. DCE off hook. DCE  
connected to Telco. Local phone provided with power to detect  
hook condition. (Implemented as 5. Speaker jack determines.)  
Internal microphone and external speaker connected to Telco.  
Squelching active. DCE off hook. DCE connected to Telco. Local  
phone provided with power to detect hook condition. (Implemented  
as 7. Speaker jack determines.)  
External microphone connected to DCE. DCE on hook. Local  
phone connected to Telco. (Implemented as 6. Mic jack  
determines.)  
External microphone and internal speaker connected to Telco.  
Squelching active. DCE off hook. DCE connected to Telco. Local  
phone provided with power to detect hook condition. (Implemented  
as 7. Mic jack determines.)  
MST  
S1  
+VLS=m  
0
S1T  
10  
11  
12  
MS1T  
M1  
M1ST  
External microphone and external speaker connected to Telco.  
Squelching active. DCE off hook. DCE connected to Telco. Local  
phone provided with power to detect hook condition. (implemented  
as 7)  
13  
M1S1T  
Handset or headset connected to DCE. DCE on hook. Local phone  
connected to Telco.  
Handset or headset connected to Telco. DCE off-hook. DCE  
connected to Telco. Local phone provided with power to detect  
hook condition.  
14  
15  
H
HT  
Handset or headset connected to Telco with microphone muted.  
DCE off-hook. DCE connected to Telco. Local phone provided with  
power to detect hook condition.  
16  
HT  
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
Table 25. Voice Mode Command Descriptions (Continued)  
Command  
Default  
Description  
Relay/Playback Control: (cont.)  
Voice I/O Primitive Codes  
Primitive Code  
Description  
L
T
Local phone  
Telco line  
+VLS=m  
(cont.)  
0
M0  
M1  
S0  
S1  
H0  
Internal microphone  
External microphone  
Internal speaker (requires squelch on any microphone activity)  
External speaker (requires squelch on any microphone activity)  
External microphone and speaker combination (handset or headset)  
NOTE: For speakerphone applications, see ATI10, +VSP, and Speakerphone AT Command  
Requirementsin the Voice Application Note for more details.  
Automatic Hang-Up Control: This command changes the way the modem responds to hang-up  
commands after it switches from voice mode to fax or data modes.  
Range: 02  
+VNH=m  
0
0*  
1
The modem retains automatic hang-ups as normal in data and fax modes  
The modem disables automatic hang-ups usually found in non-voice modes  
2
The modem disables all automatic hang-ups usually found in non-voice modes except a  
logicalhang-up  
Ringback-Goes-Away Timer: After originating a call in voice mode, this command selects the length  
of time the DCE waits between ringbacks before the DCE assumes the remote party has gone off  
hook. After dialing a phone number and detecting a ringback, the modem sends <DLE><O>to the DTE  
if another ringback is not detected within this timer value. This indicates that the remote telephone has  
been picked up (that is, gone off-hook). The ringback-goes-away timer is reset every time a new  
ringback is detected.  
+VRA=m  
50  
Range: 050 (in 100 ms increments)  
0
The DCE returns the OKcode immediately after ringback.  
50*  
(50 = 5.0 seconds)*  
Ringback-Never-Appeared Timer: This command sets the length of time the DCE waits for ringback  
when originating a call in voice mode. After dialing a phone number, the modem sends an Errorresult  
code to the DTE if ringback is not detected before the timer value elapses. This may indicate one of  
several conditions: the remote telephone was picked up before the ringback tone was generated; the  
number is no longer in service; or the number was incomplete. This timer is disabled after detecting the  
first ringback.  
+VRN=m  
10  
Range: 0255 (in 1 second increments)  
0
The DCE immediately returns the OK result code after dialing  
(10 = 10 seconds)*  
10*  
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
Table 25. Voice Mode Command Descriptions (Continued)  
Command  
Default  
Description  
Record Mode: This command causes the modem to enter record mode to record voice messages.  
Upon receiving the AT+VRX command, the modem responds to the DTE with a CONNECTmessage  
at the current DTE-to-modem rate. It is important that the UART DTE-to-modem rate be equal or  
higher to the compression-scheme-required UART data rate (for example, CL1 at 4800 samples/  
second requires 57,600 bps). If the DTE-to-modem data rate is lower than the compression-scheme-  
required UART data rate, then data may be lost or may be garbled during playback of the message.  
After sending the CONNECTmessage, the modem then sends digitized voice data that is <DLE>-  
shielded to the DTE. The modem buffers the data to ensure steady voice delivery even though the  
voice data may be transferred to the DTE in bursts. The DTE may use the <DLE><NUL> shielded code  
as a no-operation command to refresh the inactivity timer.  
During voice receive mode, the modem informs the DTE about pertinent events that may prompt the  
DTE to terminate the voice receive state. The DCE sends <DLE>codes for detection of signals such as  
busy tone, dial tone, DTMF tone, and codes for Presumed End of Messageor Presumed Hang-up.’  
Record mode is terminated whenever the modem issues a <DLE><ESC>command or provides a DTE/  
DCE inactivity timer time-out. Upon detecting the terminating character, the modem stops sampling the  
analog data. The modem then terminates record mode by sending the remaining voice data stored in  
its internal buffer, <DLE><ETX>, and an OKmessage to the DTE.  
+VRX  
none  
In some situations, the application software may want to abort record mode and immediately perform a  
new function without first reading all the recorded voice data from the modems internal buffer (for  
example, after detecting fax calling tone). This is accomplished by sending <DLE><!>to the modem  
while in record mode. Upon seeing <DLE><!>, the modem terminates record mode, clears the  
modems internal record buffer, and issues a <DLE><ETX>to the DTE followed by an OKmessage.  
The modem may immediately abort record mode if it receives either an AT+VIT=m time-out or a DTR  
toggle. If +VIT0 and the modem has not received any data or a <DLE><NUL>code before the +VIT  
timer times out, then the modem immediately aborts record mode. The modem then hangs up the line  
and changes to data mode (+FCLASS=0). If the UART DTR signal is toggled on-off-on, then the  
modem follows the &Dn setting. If configured for &D2 or &D3, the modem immediately aborts record  
mode, hangs up the line, and changes to data mode (+FCLASS=0).  
NOTE: The voice sampling rate and sampling mode must be the same values as used during record  
mode.  
Silence Detection (Quiet and Silence): This command allows the DTE to set two parameters: <sds>  
reports the sensitivity for silence detection, and <sdi> reports the length of silence required for the  
DCE to report silence when receiving voice.  
The <DLE><s>silence timer starts immediately after entering record mode. The modem stops using  
the <DLE><s>timer and starts using the <DLE><q>timer if:  
the <DLE><s>silence timer has timed out and a <DLE><s>code has been sent to the DTE, or  
if noise or voice energy has been detected above the silence detection threshold (as defined by  
<sds>).  
m = <sds>, <sdi>  
Defaults: m = 128, 50  
+VSD=m  
see m’  
<sds> Silence Sensitivity: If the received analog signal stays below this specified level for a user-  
specified time delay, the modem sends <DLE><q>to the DTE. The modem sends only one <DLE><q>  
to the DTE each time record mode +VRX is entered.  
Range: 121131  
128*  
Nominal level  
<sdi> Length of Silence: This parameter sets the period of silence that must elapse before the DCE  
reports silence (as detected by Quietor Silence).  
Range: 0255 (units of 0.1 second)  
0
Silence detection disabled  
Silence detection enabled  
50*  
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
Table 25. Voice Mode Command Descriptions (Continued)  
Command  
Default  
Description  
Compression Method Selection: This command contains four parameters that specify the voice  
compression method, voice sampling rate, silence compression sensitivity, and the degree of silence  
expansion. The DCE can support different capabilities for each compression method.  
m= <cml>, <vsr>, <scs>, <sel>  
Defaults: m = 140, 8000, 0, 0  
<cml> Compression Method: This parameter selects a voice compression method. The DTE can  
obtain the label and a string constant identifier by using the +VSM? command.  
Range: 02, 128, 129, 132, 140, 141  
0
LIN1: 8-bit Linear PCM (pulse code modulation) sampling using twos-complement  
signed numbers  
1
LIN2: 16-bit Linear PCM sampling using unsigned numbers  
2
AD4: 4-bit Adaptive differential pulse code modulation  
128  
LIN1: 8-bit Linear PCM (pulse code modulation) sampling using twos-complement  
signed numbers  
129  
132  
140*  
141  
LIN2: 16-bit Linear PCM sampling using unsigned numbers  
AD4: 4-bit Adaptive differential pulse code modulation  
CL1: 8-bit Intel A-law  
AD3: 3-bit Adaptive differential pulse code modulation  
manufac-  
turer-  
specified  
<vsr> Sampling Rate: This parameter selects the DCE voice sampling/digitizing rate for the voice  
signal. The supported sampling rates are dependent on the compression schemes used. Use the  
+VSM=? command to obtain supported sampling rates.  
+VSM=m  
Range: 4800, 7200, 8000, and 11025 samples/second  
4800  
7200  
8000*  
9600  
11025  
Default used by previous Intel modems  
Used by some bulletin boards  
Used by many Windows* WAV files  
<scs> Silence Sensitivity: The function of this parameter depends on whether the DTE is  
transmitting or receiving in voice mode. The DTE can modify the silence expansion using the <sel>  
parameter. When transmitting voice, a non-zero value of this parameter informs the DCE that the data  
stream was recorded with silence compression.  
Transmission: Range: 0  
0*  
Disabled  
When receiving voice, this parameter changes the level of noise that the DCE treats as silence. A  
higher nnumber raises the threshold of noise detection.  
Reception: Range: 0  
0*  
Disables DCE silence compression  
Raises noise detection threshold  
increments of 1  
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
Table 25. Voice Mode Command Descriptions (Continued)  
Command  
Default  
Description  
Compression Method Selection: (cont.)  
<sel> Silence Expansion: This command enables the DTE to modify the amount of silence  
expansion. This parameter represents the maximum period of silence the DCE expands a period of  
silence compressed by the <scs> parameter. The DCE ignores the <sel> parameter if <scs> is zero.  
<vsr>  
Sampling  
Rate  
<cml>  
Compression  
Serial  
UART  
Hard Disk  
(Bytes/sec.)  
Note  
Data Rate (bps) Data Rate (bps)  
<cml> = CL1*  
4800  
48,000  
72,000  
80,000  
96,000  
110,250  
57,600  
4800  
7200  
8000  
9600  
11025  
115,200  
115,200  
115,200  
115,200  
7200  
8000  
9600  
11,025  
1
1
1
1
<cml> = AD3  
<cml> = AD4  
<cml> = LIN1  
4800  
7200  
8000  
9600  
11025  
18,000  
27,000  
30,000  
36,000  
41,344  
19,200  
38,400  
38,400  
38,400  
57,600  
1800  
2700  
3000  
3600  
4135  
manufac-  
turer-  
specified  
+VSM=m  
(cont.)  
4800  
7200  
8000  
9600  
11025  
24,000  
36,000  
40,000  
48,000  
55,125  
38,400  
38,400  
57,600  
57,600  
57,600  
2400  
3600  
4800  
4800  
5513  
4800  
7200  
8000  
9600  
11,025  
48,000  
72,000  
80,000  
96,000  
110,250  
57,600  
4800  
7200  
8000  
9600  
11,025  
115,200  
115,200  
115,200  
115,200  
1
1
1
1
<cml> = LIN2  
4800  
96,000  
115,200  
9600  
1
NOTES:  
1. Because of the high UART data rates, these compression/sample rates may not be applicable to  
the serial host interface (that is, serial box modem) designs (see ATI5 to determine if the modem is  
using the serial host interface). For parallel and PC Card host interfaces, the modem ignores the  
UART data rate.  
2. DTMF detection is provided for all sample rates.  
Speakerphone On/Off Control: This command turns on the speakerphone function. This feature  
provides full-duplex speakerphone capabilities with internal adaptive echo cancellers. This command  
takes the received voice signal and loops it back to the analog transmit pins. The host must configure  
the relays and microphone interface as necessary using the AT+VLS=m command. Typically, this  
means setting the off-hook relay driver, speaker, and microphone inputs with AT+VLS=13.  
After enabling the speakerphone mode (+VSP=1), the modem remains in voice command mode and  
provides information about local off-hook detection, DTMF detection, and tone detectionif supported  
by the modem board.  
+VSP=m  
0
Range: 0, 1  
0*  
1
Speakerphone mode disabled  
Speakerphone mode enabled  
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
Table 25. Voice Mode Command Descriptions (Continued)  
Command  
#VSPS=m  
Default  
Description  
Speakerphone Type Selection: This command determines which speakerphone type is used when  
the modem receives a +VSP=m command. This allows the application software to select whether  
telephone emulation or digital speakerphone is used for +VSP=m. Upon powering-up, the modem  
determines whether it can support a digital speakerphone mode. If digital speakerphone is supported,  
then the factory default value is equal to 1. If the digital speakerphone is not supported, then the  
factory default is 0.  
1
Range: 0, 1  
0
Telephone Emulation Mode speakerphone  
Digital speakerphone  
1*  
Beep Tone Duration Timer: This command sets the default duration of all DTMF tones.  
Range: 5255 (units of 0.01 seconds)  
+VTD=m  
100  
100*  
Default value (1 second)  
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
Table 25. Voice Mode Command Descriptions (Continued)  
Command  
Default  
Description  
DTMF and Tone Generation: This command causes the modem to generate DTMF tones or pulse  
tones in voice mode. The <DLE><!>code aborts the playback of tones, sends the OKresult code,  
and returns the modem to the voice command state. The DTE/DCE inactivity timer is in place during  
tone production. The command +VTS sent without a parameter assumes the default value, which is a  
null string. The DTE may use the <DLE><NUL>-shielded code to refresh the timer.  
m=<string> The <string> is made up of a list of <freq> and <duration> parameters. <freq> is in units of  
Hz, and <duration> is in units of 0.01 seconds.  
The tone string consists of up to three types of elements: a single ASCII character, a string in brackets,  
and a string in braces. Commas must separate the elements. Missing elements assume the value of  
zero. The following list explains each element and how it can be used.  
1. Single ASCII character in the set, 09, #, *, ! and A-D, which is interpreted as a single DTMF tone.  
DTMF tones are sent as a single element expressed in the form:  
AT+VTS=<DTMF or !>  
For example, to send a DTMF 1 tone, issue AT+VTS=1to the modem.  
2. String drawn from the first set but not including a flash hook code !and enclosed in brackets [  
],which can produce a single or dual tone. The string includes three parameters, which set the  
frequency of two non-standard DTMF or single tones and a common duration for both. The quantity  
in brackets consists of a three-element list that is expressed in the following format:  
AT+VTS=[<first tone freq 1>, <second tone freq 2>,  
<duration>]  
If the duration is not specified in the <duration> parameter, the modem sends tones for the duration  
specified by the +VTD=m command.  
a. Single tones can be sent in brackets using the following format:  
+VTS=m  
none  
AT+VTS=[<first tone freq 1>]  
or  
AT+VTS=[<first tone freq 1>, <space>, <duration>]  
For example: AT+VTS=[3000] This sends a single tone of 3000 Hz with a default duration  
specified by +VTD=m.  
For example: AT+VTS=[3000,,50]  
This sends a single tone of 3000 Hz with a duration of 500 ms (50 x 0.01 second).  
b. Dual tones may be sent using the following format:  
AT+VTS=[<first tone freq 1>,<second tone freq 2>]  
or  
AT+VTS=[<first tone freq 1>,<second tone freq 2>,  
<duration>]  
For example: AT+VTS=[3000,3300]  
This sends a dual tone of 3000 Hz and 3300 Hz with the default duration set by the +VTD=m  
command.  
For example:AT+VTS=[3000,3300,50]  
This sends a dual tone of 3000 Hz and 3300 Hz with a duration of 500 ms (50 x 0.01 second).  
c. This command can be used to send a period of silence in a tone string. Use the following format:  
AT+VTS=[ , ,<duration>]  
AT+VTS=[ ]  
For example: AT+VTS=[ , ,50]  
This sends a 500 ms period of silence.  
NOTE: An asterisk (*) denotes the factory-default setting.  
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IS-101 Voice Mode AT Commands  
Table 25. Voice Mode Command Descriptions (Continued)  
Command  
Default  
Description  
DTMF and Tone Generation: (cont.)  
3. Single DTMF tones or hook flashes are sent enclosed in braces { }. A duration must be included,  
as the duration set in +VTD=m does not apply.  
Use the following format:  
AT+VTS={<DTMF or !>,<duration>}  
For example: AT+VTS={2,30}  
This command sends DTMF tone 2 with a duration of 300 ms.  
For example: AT+VTS={!,50}  
This command sends a hook flash with a duration of 500 ms.  
Send multiple DTMF signals and tones by combining elements in a given +VTS=m command  
string.  
For example:  
AT+VTS={!,30}, 1, 2, [1000,1300,50], !, {*,6}, [1000], 9  
+VTS=m  
(cont.)  
This command line programs the following events:  
none  
1. Hook-flash with a duration of 300 ms.  
2. Send DTMF 1 for the duration specified by +VTD command.  
3. Send DTMF 2 for the duration specified by +VTD command.  
4. Send tone pair 1000 Hz and 1300 Hz for a duration of 500 ms.  
5. Hook-flash with a duration specified by +VTD command.  
6. Send DTMF * for a duration of 60 ms.  
7. Send tone 1000 Hz for a duration specified by the +VTD command.  
8. Send DTMF 9 for the duration specified by +VTD command.  
For example:  
AT+VTS=1, [, ,50], 2, [ ], 9  
This command line programs the following events:  
1. Send DTMF 1 for the duration specified by +VTD command.  
2. Play silence for a duration of 500 ms.  
3. Send DTMF 2 for the duration specified by +VTD command.  
4. Play silence for a duration specified by +VTD command.  
5. Send DTMF 9 for the duration specified by +VTD command.  
Play Mode: This command causes the modem to start voice transmission (playback mode) and play  
back a previously recorded voice message.  
Upon receiving the AT+VTX command, the modem responds to the DTE with a CONNECTmessage  
at the current DTE-to-modem rate. It is important that the UARTs DTE-to-modem rate be equal to or  
higher than the compression-scheme-required UART data rate (for example, CL1 at 4800 samples/  
second requires 57,600 bps). If the DTE-to-modem data rate is lower than the compression-scheme-  
required UART data rate, then data may be lost or the playback message may be garbled. After  
receiving the CONNECTmessage, the DTE then sends the voice file to the modem. To ensure that  
data is not overwritten, the modem provides both hardware or software flow control with AT+FLO=m.  
The modem also buffers the data to ensure steady voice delivery, even though the voice data may be  
transferred from the DTE in bursts.  
Playing mode is terminated when the data is exhausted and the modem receives the two terminating  
characters <DLE><ETX>from the DTE. Upon detecting <DLE><ETX>, the modem issues an OKresult  
code. After the modems internal buffer is empty, it returns to the command mode.  
+VTX  
none  
To abort playback mode immediately without waiting for the modem to empty its internal buffer, send  
<DLE><CAN><DLE><ETX>.The modem aborts playback mode immediately in two other situations:  
during a AT+VIT=m time-out or a DTR toggle. The modem immediately aborts playback mode if  
+VIT0 and the modem has not received any data or if the modem receives a <DLE><NUL>code  
before the +VIT timer time-out. The modem then hangs up the line and switches to data mode  
(+FCLASS=0). If the UART DTR signal is toggled from on-off-on, then the modem follows the &Dn  
setting. If configured for &D2 or &D3, then the modem immediately aborts playback mode, hangs up  
the line, and switches to data mode (+FCLASS=0).  
NOTE: The voice sampling rate and sampling mode must be the same values used during record  
mode.  
NOTE: An asterisk (*) denotes the factory-default setting.  
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S-Registers  
S-Registers  
7
The 536EX chipsets provide direct access to the internal registers known as S-registers. The DTE  
uses S-registers to set up and check modem configurations. The contents of these registers can be  
changed using the ATSn=x command, where nis the register number and xis the value to be  
stored. The contents of the S-registers can be read using the ATSn? command. Most S-registers  
can be read from or written to; however, some S-registers (such as S14) are read-only. Writing to a  
read-only register may cause the modem to act improperly (that is, even though the contents of a  
read-only S-register may be changed using the ATSn=x command, changing the contents of the S-  
register does not normally configure the entire modem).  
Reserved S-registers are used by the modem and provide no valuable information to the DTE.  
These registers have been removed from the following table. Reserved S-registers should never be  
written to, as they cause the modem to lock up.  
Table 26. S-Register Command Descriptions  
Command  
Default  
Description  
Number of Rings to Auto-Answer On: Assigning S0 a value from 1 to 255 configures the  
modem for auto-answer mode. The modem automatically goes off-hook and initiates a data  
mode-answer mode handshake after detecting the specified number of rings. This S-register is  
meant for data modem mode only and should be set to 0for fax and voice modes.  
Range: 0255 rings  
0
Auto-answer mode disabled  
Auto-answer mode enabled  
S0  
0
1255  
NOTES:  
If Caller ID is enabled (+VCID=m), then the modem only answers after the second ring  
even if S0=1.  
Setting n > 2 causes the modem to answer on the nth ring signal.  
Ring Count: Reports the number of ring signals detected by the modem. This register is cleared  
to zero if no new ring signals are detected within an 8 second time interval.  
S1  
S2  
0
Range: 0255 rings  
Default: 0 rings  
Escape Character: S2 specifies an ASCII value for the Hayes or TIES escape character. The  
factory default is +or ASCII decimal 43. The escape character may range between 0127. Any  
value over 127 disables the escape sequence.  
43  
Range: 0127  
Default: 43 (+)  
Carriage Return Character: S3 specifies the AT command string terminator and modem  
response code terminator. The factory default is a <CR> or carriage return (ASCII decimal 13).  
S3  
S4  
13  
10  
Range: 0127  
Default: 13 (carriage return)  
Line Feed Character: S4 specifies the line feed character, which is used for verbose (text)  
modem result codes.  
Range: 0127  
Default: 10 (line feed)  
NOTE: An asterisk (*) denotes the factory-default setting.  
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S-Registers  
Table 26. S-Register Command Descriptions (Continued)  
Command  
Default  
Description  
Backspace Character: S5 specifies the backspace character that is used to delete the last-  
entered character. After receiving a backspace character, the modem sends three characters to  
the DTE: a backspace character, a space character, and then another backspace character.  
S5  
8
Range: 032, 127  
Default: 8 (BS)  
Wait Before Blind Dialing: S6 specifies the amount of time that must elapse after the modem  
goes off-hook before the modem starts dialing the first telephone number. The modem waits for  
at least 2 seconds before dialing the first number, even if S6 is set for a value less than 2. S6 is  
only used for result code type commands X0, X1, and X3 (that is, blind-dialing types of result  
codes). Result code types X2 and X4 enable dial-tone detection and ignore the contents of S6.  
S6  
2
Range:  
2255 seconds  
Default: 2 seconds  
Wait for Carrier/Dial Tone: S7 specifies the length of time that the modem waits to detect the  
remote modem carrier after dialing the telephone number. If the remote modem carrier is not  
detected within the S7 time limit, the modem hangs up and sends a NO CARRIERresponse  
code to the DTE. If the remote modem carrier is detected, the modem goes into online data  
mode and sends a CONNECTmessage to the DTE.  
S7  
60  
S7 also specifies the time duration for the @(wait for quiet answer) dial modifier.  
Range:  
1255 seconds  
Default: 60 seconds  
Pause Time for Dial Modifier: S8 specifies the length of time that the modem pauses during  
the dialing process each time the ,dial modifier is detected in the dialing string.  
S8  
S9  
2
6
Range:  
0255 seconds  
Default: 2 seconds  
Carrier Detect Recovery Time: S9 specifies how long the remote modem carrier must be  
present on the telephone line before the modem detects it and turns on DCD. The greater the  
time duration, the less likely that a false carrier detection occurs due to noise on the telephone  
line.  
Range:  
Default:  
1255 (1/10 of a second)  
6 (equals 0.6 seconds)  
Lost Carrier Hang Up Delay: For modes V.32 and below, S10 specifies the length of time the  
modem waits before hanging up after the loss of the remote modem carrier. This delay allows  
for the temporary loss of the remote modem carrier without causing the local modem to hang  
up.  
S10 reports the time in 1/10 second units beyond 20 seconds. For example, when S10 = 0, the  
wait time is 20 seconds. When S10 = 100, the wait time is 30 seconds.  
In V.34 and V.90 modes, the modem automatically retries the connection for the time specified  
in S10 (Plus the mode-specific base time) before hanging up. In V.34 mode, the base time is 20  
seconds. In V.90 mode the base time is 45 seconds.  
S10  
14  
For all modes, the modem does not disconnect upon loss of the remote modem carrier if S10 is  
255.  
Range:  
Default:  
0255 (1/10 of a second)  
14 (equals 1.4 seconds plus the 20 second minimum)  
DTMF Dialing Speed: S11 specifies the duration of dual-tone multi-frequency (DTMF) dialing.  
This register is not used for pulse dialing.  
S11  
70  
Range: 50255 ms  
Default: 70 ms  
NOTE: An asterisk (*) denotes the factory-default setting.  
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S-Registers  
Table 26. S-Register Command Descriptions (Continued)  
Command  
Default  
Description  
Guard Time: S12 is used to specify guard and detect times used for the Hayes and TIES  
escape sequences.  
For the Hayes Escape Sequence, S12 specifies the minimum-delay timer (or guard time) before  
and after the three escape characters that is required for the modem to detect the Hayes  
Escape Sequence.  
S12  
50  
For TIES, S12 specifies the maximum time limit that must elapse after receiving the three  
escape characters (and no other characters) before sending an OK message to the DTE.  
Range:  
Default:  
0255 (1/50 of a second)  
50 (equals 1 second)  
Bit-Mapped Options: S14 is a read-only register that indicates AT command settings.  
Bit 0  
Bit 1  
Reserved  
0
1*  
E0 is selected  
E1 is selected  
Bit 2  
Bit 3  
0*  
1
Q0 is selected  
Q1 is selected  
0
1*  
V0 is selected  
V1 is selected  
S14  
138  
Bit 4  
Bit 5  
Reserved  
0*  
1
T (tone) dial is selected  
P (pulse) dial is selected  
Bit 6  
Bit 7  
Reserved  
0
Answer  
1*  
Originate  
Modem Test Options: S16 indicates the test in progress.  
Bit 0  
0*  
1
Local analog loopback disabled  
Local analog loopback enabled (&T1)  
Bit 1  
Reserved  
Reserved  
S16  
0
Bit 25  
Bit 6  
0*  
1
Analog loopback with self-test disabled  
Analog loopback with self-test enabled (&T8)  
Bit 7  
0*  
1
Reserved  
Reserved  
Modem Test Timer: S18 specifies the length of time that the modem conducts a data mode  
(except for V.90 and V.92) loopback test using the &Tn command. After timing out, the modem  
returns to command mode. Setting S18 to 0disables the modem test timer; the loopback test  
must be terminated by issuing the appropriate escape sequence followed by an AT&T0 or ATH.  
S18  
0
Range:  
0255 seconds  
Default: 0 seconds  
NOTE: An asterisk (*) denotes the factory-default setting.  
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S-Registers  
Table 26. S-Register Command Descriptions (Continued)  
Command  
Default  
Description  
Bit-Mapped Options: S21 is a read-only register that indicates AT command settings.  
Bit 0  
Reserved  
Reserved  
Reserved  
Bit 1  
Bit 2  
Bits 43  
00  
01  
10*  
11  
&D0 is selected  
&D1 is selected  
&D2 is selected  
&D3 is selected  
S21  
48  
Bit 5  
Bit 6  
Bit 7  
0
1*  
&C0 is selected  
&C1 is selected  
0*  
1
&S0 is selected  
&S1 is selected  
0*  
1
Y0 is selected  
Y1 is selected  
Bit-Mapped Options: S22 is a read-only register that indicates AT command settings.  
Bits 10  
Bits 32  
Bits 64  
00  
01  
10*  
11  
L0 is selected  
L1 is selected  
L2 is selected  
L3 is selected  
00  
01*  
10  
11  
M0 is selected  
M1 is selected  
M2 is selected  
M3 is selected  
S22  
118  
000 X0 is selected  
001 Reserved  
010 Reserved  
011 Reserved  
100 X1 is selected  
101 X2 is selected  
110 X3 is selected  
111* X4 is selected  
Bit 7  
0*  
1
&P0 is selected  
&P1 is selected  
Detect DTR Change: S25 defines the minimum amount of time that DTR has to remain off (that  
is, on-to-off-to-on transitions) before the modem performs the function specified by &Dn  
command. A change in DTR that persists for a shorter time than the value specified in S25 is  
ignored by the modem (see the &Dn command).  
S25  
S30  
5
0
Range: 0255 (1/100 of a second)  
Disconnect Inactivity Timer: This S-register sets the length of time (in minutes) that the  
modem stays online/off-hook before disconnecting when no data is being transmitted or  
received. In data and fax modes, any data transmitted or received between the DTE-DCE  
interface resets the timer. In all other modes (except Telephone-Emulation mode), any data  
transmitted resets the timer. In Telephone-Emulation mode, S30 is ignored (that is, the modem  
does not automatically hang up the line after a given time delay).  
Range: 0255 minutes  
0
Disabled  
NOTE: An asterisk (*) denotes the factory-default setting.  
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S-Registers  
Table 26. S-Register Command Descriptions (Continued)  
Command  
Default  
Description  
Sleep Mode Timer: S33 determines when the modem enters sleep or power-down mode.  
When enabled (S33 0), the controller enters sleep mode whenever the modem has been  
inactive for a user-programmable time delay (S33). The modem is considered to be in an  
inactive state when:  
No internal processing is being performed;  
No activity occurs between the host and the modem within a  
specified time period;  
S33  
10  
The modem is off-line.  
The modem exits sleep mode whenever the host reads or writes to the  
modem or when a ring signal is detected.  
Sleep mode is disabled by setting S33 to 0.  
Range: 090 seconds  
NOTE: An asterisk (*) denotes the factory-default setting.  
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Caller ID  
Caller ID  
8
This section describes Caller ID for the United States. Caller ID is a service that lets the called  
party know the telephone number of the caller before the call is answered. The information  
transmitted to the called party via Caller ID includes the callers name, call date, the call time, and  
the call number. This service is not available everywhere due to central office telephone equipment  
limitations and legal prohibition in some locations.  
The +VCID = n command controls the reporting and presentation of data associated with the  
Caller ID services in United States and Canada in the ICLID (incoming call line ID) data format.  
The ICLID data comes in one of two formats: SDM (single data message) format or MDM  
(multiple data message) format. In both formats, data is provided as data items and packet control  
information.  
When enabled, the DCE reports any Caller ID information detected after the first ring message  
(note that more <CR> <LF> combinations may occur after the RING result code). All data items  
are reported using the <tag> <=> <value> pair format. Spaces are present on both sides of the equal  
sign.  
This chipset allows for two types of Caller ID reporting formats, formatted and unformatted. In  
formatted reporting, DCE does not report any Caller ID information if a check sum error is  
detected in the Caller ID packet. If the DCE receives multiple copies of the Caller ID packets, the  
DCE sends only one of the correct packets to the DTE. If the DCE has never presented a correct  
packet but has received the line seizure information at least once, the DCE returns <MESG> <=>  
<CALID_202>.  
The DCE breaks up the presentation of the date and time into two separate <Tag><Value> pairs for  
those data items where the date and time appear together.  
Table 27. Caller ID Tags for Formatted Reporting  
Tag  
Description  
DATE = MMDD where MM is the month number, 01 through 12, and DD is the day number, 01  
through 31. All numbers are in ASCII decimal. For numbers less than 10, a filling ASCII zero is used.  
DATE  
TIME = HHMM where HH is the hour number, 00 through 23, and MM is the minute number, 00  
TIME through 59. All numbers are in ASCII decimal format. For numbers less than 10, a filling ASCII zero is  
used.  
NMBR = <number> or P or O (ASCII 4Fh) where <number> is the telephone number of the caller,  
where P indicates that the calling number information is not available since the originating caller has  
requested private service, and where O indicates that the calling number information is not available  
NMBR  
since the out of area code or the service is unavailable.  
NAME NAME = <listing name> where <listing name> is the subscription listing name.  
MESG = <data tag> <length of message> <data> <checksum> in printable ASCII (to avoid possible  
problems with binary output numbers).  
MESG  
If a data tag is unrecognizable, the DCE presents the given data items information using the  
MESG tag. The DCE follows the conventions of the unformatted reporting form (defined below)  
where applicable for the given data item only.  
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Caller ID  
Example 1: The following example of formatted form report (AT+VCID=1) illustrates the case  
when the DCE does not recognize the tag of one given data item from a packet of data items (data  
or fax command mode).  
RING  
DATE = 0321  
TIME = 1405  
NMBR = 5045551234  
NAME = DOE JOHN  
MESG = 060342424231  
RING  
RING  
Example 2: The following example illustrates the unsolicited response (AT+VCID=1) form of  
voice mode (voice, command, playback, and record modes).  
<DLE> R  
<DLE> X  
DATE = 0321  
TIME = 1405  
NMBR = 5045551234  
NAME = DOE JOHN  
MESG = 060342424231  
<DLE> .  
<DLE> R  
<DLE> R  
Example 3: The following example of formatted form reporting illustrates the case when the DCE  
does not recognize the tag of the packet (data or fax command mode).  
RING  
MESG = 060342424231  
RING  
RING  
For unformatted form reporting (AT+VCID=2), the DCE presents all information contained in the  
Caller ID packet as ASCII hex in printable characters. This information includes all message type  
information, message length, data and checksum.  
Example 4: The following example illustrates unformatted form reporting (data or fax command  
mode).  
RING  
MESG = 04123033323131334303539313435353132333435  
RING  
RING  
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Parallel Host Interface 16C450/16C550A UART  
Parallel Host Interface 16C450/16C550A  
UART  
9
9.1  
UART Emulation in the Controllerless Modem  
When controllerless modems are used with Windows applications, the communication driver  
architecture eliminates the need for a UART emulation (see Section 1.1, Controllerless Modem  
Driver Overviewon page 7). However, MS-DOS applications used with controllerless modems  
retain the need for a UART emulation. Therefore, Intel provides the Intelsdb.VXD driver, which  
includes this UART emulation and also interacts directly with the Windows VCOMM.VxD driver  
(see Figure 11).  
Figure 11. UART Emulation in Intelsdb.VxD  
MS-DOSAPPLICATION  
WINDOWSAPPLICATION  
Intelsdb.VXD  
UART EMULATION  
HAM PORT DRIVER  
VCOMM.VXD  
The parallel host interface of the FastPath family emulate the electrical and register functions of a  
16550A and 16C450 UART. Upon modem reset, the modem defaults to a 16C450. The host (DTE)  
can then configure the UART to function as a 16C550A UART.  
In 16C450 emulation mode, the DTE and modem transfer data back and forth a byte at a time. In  
16C550A emulation mode, the modem provides two 16-byte FIFO buffers, one for the transmitter  
and another for the receiver. Thus, up to 16 bytes of data may be sent to or received from the  
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Parallel Host Interface 16C450/16C550A UART  
modem for each data interrupt, instead of only a single byte, as in 16C450 mode. The following  
diagram shows how the FIFO is used. Host software using this FIFO capability can significantly  
reduce system overhead by reducing the number of times that interrupt service routines are called.  
Figure 12. FIFO Buffers for Transmitter and Receiver  
UART  
Transmitter  
Holding  
Register  
(THR)  
Modem  
Host  
Transmitter  
Shift  
Register  
Modem Transmitter FIFO  
(DTE)  
UART Transmitter Flow Diagram  
UART  
Receiver  
Buffer  
Modem  
Receiver  
Shift  
Host  
Modem Receiver FIFO  
(DTE)  
Register  
Register  
(RBR)  
UART Receiver Flow Diagram  
The register addresses are divided into two types: single-register access and multiple-register  
access. Most of the UART registers are single-register access (that is, only one internal register is  
accessible for a given register address). UART register addresses 37 are used to access a single  
internal register. The remainder of the UART register addresses (02) are used to access two or  
more internal registers.  
Register address 2 is used to write FIFO control information into the FCR (FIFO Control register)  
and to read the IIR (Interrupt Identity register).  
Register address 1 is used to read and write data to the IER (Interrupt Enable register) [when  
DLAB = 0] and the MS DLM (Divisor Latch register) [when DLAB = 1].  
Register address 0 is used to read data from the RBR (Receiver Buffer register) [when DLAB = 0],  
write data to the THR (Transmitter Holding register) [when DLAB = 0], and read and write to the  
LS DLL (Divisor Latch register) [when DLAB = 1]. The UART registers and FIFO usage are  
described in the following sections.  
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Figure 13. Parallel Host Interface UART Register Bit Assignments  
BIT NUMBER  
REGISTER  
NAME  
REGISTER  
ADDRESS  
7
6
5
4
3
2
1
0
Scratch  
register  
(SCR)  
7
6
Scratch register (SCR)  
Delta  
Data  
Carrier  
Detect  
(DDCDD)  
Trailing  
Edge of  
Ring  
Indicator  
(TERI)  
Delta  
Data  
Set  
Ready  
(DDSR)  
Delta  
Clear  
to  
Send  
(DCTS)  
Modem  
Status  
register  
(MSR)  
Clear  
to  
Send  
Data  
Carrier  
Detect  
(DCD)  
Data  
Set  
Ready  
Ring  
Indicator  
(RI)  
(CTS)  
(DSR)  
Transmitter  
Holding  
register  
Empty  
Error in  
RCVR  
FIFO  
Line  
Status  
register  
(LSR)  
Transmitter  
Empty  
(TEMT)  
Data  
Ready  
(DR)  
Break  
Interrupt  
(BI)  
Framing  
Error  
(FE)  
Parity  
Error  
(PE)  
Overrun  
Error  
(OE)  
5
4
(Note 1)  
(THRE)  
Modem  
Control  
register  
(MCR)  
Request  
to  
Send  
Data  
Terminal  
Ready  
(DTR)  
0
0
0
Loop  
Out 1  
Out 2  
(RTS)  
Divisor  
Latch  
Access  
bit  
Word  
Length  
Select  
bit 1  
Word  
Length  
Select  
bit 0  
Number  
of  
Stop bits  
Line  
Even  
Parity  
Select  
(EPS)  
Parity  
Enable  
(PEN)  
Stick  
Parity  
(SPAR)  
Set  
Break  
(SBRK)  
Control  
register  
(LCR)  
3
2
2
(STB)  
(DLAB)  
(WLS1)  
(WLS0)  
FIFO  
Control  
register  
[write only]  
(FCR)  
XMIT  
FIFO  
Reset  
RCVR  
FIFO  
Reset  
RCVR  
Trigger  
(MSB)  
RCVR  
Trigger  
(LSB)  
FIFO  
Enable  
(FIFOE)  
Reserved  
Reserved  
Reserved  
(XFIFOR)  
(RFIFOR)  
Interrupt  
Identity  
register  
[read only]  
(IIR)  
FIFOs  
Enabled  
(Note 1)  
FIFOs  
Enabled  
(Note 1)  
Interrupt  
ID  
bit 2  
0if  
Interrupt  
pending  
Interrupt  
ID  
bit 1  
Interrupt  
ID  
bit 0  
0
0
(Note 1)  
Transmitter  
Holding Reg.  
Empty  
Int. Enable  
(THREIE)  
Receiver  
Line Status  
Interrupt  
Enable  
Modem  
Status  
Interrupt  
Enable  
(MSIE)  
Received  
Data  
Available  
Int. Enable  
(RDAIE)  
Interrupt  
Enable  
register  
(IER)  
1
0
0
0
0
DLAB=0  
(RLSIE)  
Transmit  
Holding  
register  
[write only]  
(THR)  
0
Transmit Holding register (THR) [Write only]  
Receiver Buffer register (RBR) [Read only]  
DLAB=0  
Receiver  
Buffer  
register  
[read only]  
(RBR)  
0
DLAB=0  
Divisor  
Latch  
(MS)  
1
MS Divisor Latch (DLM)  
LS Divisor Latch (DLL)  
DLAB=1  
(DLM)  
Divisor  
Latch  
(LS)  
0
DLAB=1  
(DLL)  
NOTE: These bits are always 0in 16C450 mode.  
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Parallel Host Interface 16C450/16C550A UART  
9.2  
UART Register Definitions  
9.2.1  
Scratch Register (SCR)  
Figure 14. Scratch Register (SCR)  
Register 7  
SCR  
This is an 8-bit read/write register used by the DTE for temporary storage of data.  
9.2.2  
Modem Status Register (MSR)  
Figure 15. Modem Status Register (MSR)  
Register 6  
DCD  
RI  
DSR  
CTS  
DDCDD  
TERI  
DDSR  
DCTS  
This register provides four bits (bits 7:4) that show current modem state and four bits (bits 3:0) that  
provide modem change information. Bits 3:0 are set to 1whenever the control information  
changes state. These bits are reset to 0whenever the DTE reads the MSR register. If the modem  
status interrupt is enabled (IER3), the modem generates an interrupt on the µP HINT pin whenever  
MSR bits 3:0 are set to 1.’  
Data Carrier Detect (DCD)When this bit is set to 1, it indicates that the remote modem data carrier has been detected  
(refer to the &C command).  
Bit 7  
Bit 6 Ring Indicate (RI)This bit indicates when a ring signal has been detected.  
Data Set Ready (DSR)This bit indicates when the modem is ready to establish a communication link.  
When entering voice mode, DSR is set to 1. DSR is used for voice playback/record DMA mode to indicate when the DTE  
Bit 5  
has not responded to a modem DMA data transfer request. DSR is set to 1 when DMA data are being transferred; DSR is  
set to 0 when a new DMA transfer has not occurred with 1.7 ms after the previous DMA transfer. DSR works similarly to a  
DMA terminal count.  
Bit 4 Clear To Send (CTS)When this bit is set to 1, it indicates to the DTE that the modem is ready to receive data.  
Delta Data Carrier Detect (DDCDD)When this bit is set to 1, it indicates that the DCD bit has changed its value since  
the DTE last read the MSR register.  
Bit 3  
Bit 2 Trailing Edge of Ring Indicator (TERI)This bit is set to 1after the RI signal goes from a high to low state.  
Delta Data Set Ready (DDSR)When this bit is set to 1, it indicates that the DSR bit has changed its value since the  
DTE last read the MSR register.  
Bit 1  
Delta Clear to Send (DCTS)When this bit is set to 1, it indicates that the CTS bit has changed its value since the DTE  
last read the MSR register.  
Bit 0  
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9.2.3  
Line Status Register (LSR)  
Figure 16. Line Status Register (LSR)  
Register 5 RCVR Err  
TEMT  
THRE  
BI  
FE  
PE  
OE  
DR  
This read-only register provides UART status information to the host. Bits 4:1 report error  
conditions. These bits are reset to 0any time the host reads this register. An interrupt is generated  
to the host whenever any one of the bits (4:1) is set to 1and the RLSIE (receiver line status  
interrupt) has been enabled. Bits 0, 5, and 6 provide status information for sending and receiving  
data through the THR (Transmit Holding register) and the RBR (Receiver Buffer register). Bits 0,  
5, 6 are reset to 1only when the host performs a specified action.  
In FIFO mode, the modem keeps track of the character in which an error has occurred and does not  
report the error to the DTE until the associated character gets to the top of the stack.  
Note: In FIFO mode, the DTE must write a data byte in the RX FIFO by the loopback mode to write to  
LSR2LSR4. LSR0 and LSR7 cannot be written to in FIFO mode.  
Error in RCVR FIFOIn 16C450 emulation mode, this bit is always a 0.  
In FIFO mode, this bit is set to 1by the DCE whenever at least one parity error, framing error, or break indication has  
occurred in the RCVR FIFO. This bit is cleared when the DTE reads the LSR register and there are no subsequent FIFO  
errors.  
Bit 7  
Bit 6  
TEMT (Transmitter Empty)This bit is set to 1by the DCE whenever the THR (Transmit Holding register) and  
transmitter shift register are empty. This bit is automatically reset to 0by the DCE whenever the host writes a byte to the  
THR.  
In FIFO mode, this bit is set to 1whenever the transmitter FIFO and shift register are both empty.  
THRE (Transmitter Holding Register Empty)This bit is set to 1whenever the THR (Transmit Holding register) is  
empty. This bit is set to 0whenever the host writes data into the THR. Additionally, if the THREIE (Transmitter Holding  
Register Empty Interrupt Enable) is set to 1, the modem causes an interrupt to the host whenever THRE goes to 1.  
Bit 5  
Bit 4  
Bit 3  
Bit 2  
In FIFO mode, this bit is set to 1whenever the XMIT FIFO is empty. This bit is then reset to 0when at least one byte is  
written to the XMIT FIFO.  
BI (Break Interrupt)This bit is set to 1whenever the received data are spaces (logic 0) for at least 2M + 3 bits (M =  
start bit + # of data character bits + parity bit + # of stop bits). This bit is reset to 0whenever the host reads the LSR  
register. The modem waits for the valid start bit, before again transferring data to the FIFO.  
When a break occurs in FIFO mode, a single null character is placed in the RVCR FIFO. The BI bit is then set when the  
zero character gets to the top of the FIFO stack.  
FE (Framing Error)This bit is set to 1whenever a valid stop bit (logic 1) has not been detected after the last data bit or  
parity bit. This bit is reset to 0whenever the host reads the LSR register. The UART tries to re-synchronize after a  
framing error.  
In FIFO mode, the modem FE bit is set to 1whenever the associated framing error character has reached the top of the  
stack.  
PE (Parity Error)This bit is set to 1whenever the received data character does not have the correct even or odd parity,  
as selected by the EPS (even parity select) bit [LCR4] and the stick parity bit [LCR 5]. This bit is reset to 0whenever the  
host reads the LSR register.  
In FIFO mode, the modem PE bit is set to 1whenever the associated framing error character has reached the top of the  
stack.  
Bit 1 OE (Overrun Error)Not supported.  
Data ReadyThis bit is set to 1whenever the modem writes a new received data character into the RBR (Receiver  
Buffer register) or FIFO. This bit is reset to 0whenever the DTE reads the RBR or FIFO.  
Bit 0  
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Parallel Host Interface 16C450/16C550A UART  
9.2.4  
Modem Control Register (MCR)  
Figure 17. Modem Control Register (MCR)  
0
0
0
Loop  
Out 2  
Out 1  
RTS  
DTR  
Register 4  
This register controls the DTE-DCE UART interface.  
Bit 7:5  
Bit 4  
Not usedThese bits are permanently set to 0.  
Loop BitWhen set to 1, this bit configures the UART for loopback diagnostic testing. In diagnostic mode,  
any data that is written to the THR (Transmit Holding register) is looped back to the RBR (Receiver Buffer  
register).  
After writing a data byte to the THR register in loopback mode, the DTE must read the RBR register before  
writing a new data byte to the THR.  
Unlike a real 16C450 UART, the modem signals OUT1*, OUT2*, RTS*, and DTR* are not looped back to the  
MSR register.  
Out 2This bit, when set to 1by the DTE, enables the HINT output pin. When set to 0, this bit causes the  
HINT pin to be in a high-impedance state.  
Bit 3  
Bit 2  
Bit 1  
Out 1This read/write bit is not used for any specific functions.  
RTS (Request to Send)This bit when set to 1, indicates that the DTE is ready to send data to the modem.  
DTR (Data Terminal Ready)When set to 1, this bit indicates that the DTE is read to establish a  
communication link.  
Bit 0  
9.2.5  
Line Control Register (LCR)  
Figure 18. Line Control Register (LCR)  
Register 3  
DLAB  
SBRK  
SPAR  
EPS  
PEN  
STB  
WLS1  
WLS0  
This register specifies the asynchronous data communication exchange format. The modem  
supports up to 10-bit data characters (1 start bit + # of data character bits + parity + # of stop bits).  
Divisor Latch Access Bit (DLAB)This bit must be set to 1to access the divisor latches of the baud rate  
generator during a read or write operation. The UART registers 1 and 0 are used for the divisor latches. This  
bit must be set to 0to access the Receiver Buffer register (RBR), the THR (Transmitter Holding register) or  
the IER (Interrupt Enable register).  
Bit 7  
Bit 6  
Bit 5  
SBRK (Set Break)This bit is used to send a long-space disconnect message to the remote modem.  
The procedure is as follows:  
After the THRE bit has been set to 1by the DCE and before setting the SBRK bit, the DTE needs to write  
a NULL ($00h) character to the THR.  
The DTE then sets the SBRK bit after the next time the THRE bit is set by the DCE (a long space is now  
being transmitted).  
To return to normal transmission mode, wait for the TEMT to be equal to 1, then reset the SBRK bit.  
SPAR (Stick Parity)When this bit is set to 1, stick parity is enabled. When configured for stick parity (SPAR  
= 1), even parity (EPS = 1) with parity enable (PEN = 1), then the parity bit is transmitted and checked as a  
logic 0. When configured for stick parity (SPAR = 1), odd parity (EPS = 0) and parity enable (PEN = 1) are set  
to 1, then the parity bit is transmitted and checked as a logic 1.  
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EPS (Even Parity Select)When even parity select (LCR4) and parity enable (LCR3) are set to 1, an even  
Bit 4  
Bit 3  
number of logic 1s are transmitted or checked. When even parity select (LCR4) is a 0and parity enable  
(LCR3) is a 1, an odd number of logic 1s are transmitted or checked.  
PEN (Parity Enable)When this bit is set to 1, a parity bit is generated (transmitted data) or checked  
(receive data) between the last data character word bit and stop bit of the serial data.  
NOTE: The parity bit is used to produce an even or odd number of 1s when the data word bits and the parity  
bits are summed.  
Number of Stop Bits (STB)This bit specifies the number of stop bits transmitted and received in each serial  
character. When STB is set to 0, one stop bit is generated for each transmitted data character. When STB is  
set to 1and the word length (WLS1 and WLS0) is equal to 6, 7, or 8 bits, then two stop bits are generated for  
each transmitted data character. When STB is set to 1and the word length (WLS1 and WLS0) is equal to 5  
bits, then one and a half stop bits are generated for each transmitted data character. The receiver only checks  
for the first stop bit, regardless of the number of stops bits transmitted.  
Bit 2  
Word Length Select Bits (WLS1 and WLS0)These two bits specify the data character word length of the  
transmitted and received data. The supported word lengths are provided below.  
Bit 1  
Bit 0  
Word Length  
Bits 1:0  
0
0
1
1
0
1
0
1
5 bits  
6 bits  
7 bits  
8 bits  
9.2.6  
FIFO Control Register (FCR)  
Figure 19. FIFO Control Register (FCR)  
RCVR Trig. RCVR Trig. Reserved Reserved  
DMA  
XFIFOR  
RFIFOR  
FIFOE  
Register 2  
(write-only)  
This write-only register is used to enable the receiver and transmitter FIFOs, clear the FIFOs, set  
the RCVR FIFO trigger level, and select the DMA signaling type.  
MSB and LSB (RCVR Trigger Bits)FCR bits 7 and 6 are used to set the trigger level for the RCVR FIFO interrupt.  
RCVR FIFO  
Trigger Level (Bytes)  
Bit 7  
Bit 6  
Bits 7:6  
0
0
1
1
0
1
0
1
01  
04  
08  
14  
Bits 5:3 ReservedBits 5, 4, and 3 are reserved for future enhancements.  
XFIFOR (XMIT FIFO Reset)When set to 1, this bit clears all the bytes in the XMIT FIFO and resets the internal  
Bit 2  
Bit 1  
Bit 0  
counter logic to 0. The internal shift register is not cleared by the XFIFOR bit. This bit is automatically cleared by the  
modem.  
RFIFOR (RCVR FIFO Reset)When set to 1, this bit clears all the bytes in the RCVR FIFO and resets the internal  
counter logic to 0. The internal shift register is not cleared by the RFIFOR bit. This bit is automatically cleared by the  
modem.  
FIFOE (FIFO Enable)This bit when set to 1, enables both the XMIT and RCVR FIFOs. This bit must be a 1’  
whenever writing to any other FIFO bit. If FIFO is not set to 1, then the DTE can not program any of the FIFO  
functions.  
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Parallel Host Interface 16C450/16C550A UART  
9.2.7  
Interrupt Identity Register (IIR)  
b
Figure 20. Interrupt Identity Register (IIR)  
Register 2  
(read-only)  
FIFO EN FIFO EN  
0
VDMA Int. ID 2 Int. ID 1 Int. ID 0 Int. Pen.  
This read-only register indicates when the transmitter and receiver FIFOs are enabled, and the  
source of highest-priority pending interrupt to the DTE. Five levels of modem interrupt sources in  
order of priority are: receiver line status, received data ready, character time-out indication,  
transmitter holding register empty, and modem status. When the DTE reads the IIR, the modem  
freezes all interrupts and indicates the highest-priority pending interrupt. While the DTE is reading  
the IIR register, the modem records new interrupts but does not change its current indication until  
the read process is completed.  
Table 28. Interrupt Control Functions  
FIFO  
Mode  
Only  
Interrupt  
Identification  
Register  
Interrupt Source and Reset Functions  
Bit 3 Bit 2 Bit 1 Bit 0  
Int.  
Priority  
Level  
Interrupt Type  
Interrupt Source  
Interrupt Reset Control  
ID 2  
ID1  
ID0 Pend.  
0
0
0
1
None  
None  
Overrun Error, Parity Error,  
Framing Error or Break  
Interrupt  
Receiver Line  
Status  
Reading the LSR (Line  
Status register)  
0
0
1
1
1
0
Highest  
Reading the RBR (Receiver  
Buffer register) or the FIFO  
Drops below the Trigger  
Level  
Received Data  
Available  
Receiver Data Available or  
Trigger Level Reached  
0
0
0
0
Second  
Second  
No characters have been  
removed from or entered  
into the RCVR FIFO during  
the last four character times,  
and there is at least one  
character in it during this  
time  
Character  
Time-out  
Indication  
Reading the RBR (Receiver  
Buffer register)  
1
1
Transmitter  
Holding  
Reading the IIR register (if  
the source of interrupt) or  
writing into the Transmitter  
Holding register  
Transmitter Holding  
Register Empty  
0
0
0
0
1
0
0
0
Third  
Register  
Empty  
Clear to Send,  
Data Set Ready,  
Reading the MSR (Modem  
Status register)  
Fourth  
Modem Status  
Ring Indicator, or Data  
Carrier Detect  
Bits 7:6 FIFOs Enable BitsThese two bits are set whenever FCR0 = 1.  
Bits 5 Not usedThis bit is permanently set to 0.  
Bit 4  
Reserved  
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Interrupt ID Bit 2In 16C450 mode, this bit is always a 0.  
Bit 3  
In FIFO mode, both this bit and bit IIR2 are set whenever a time-out interrupt is pending.  
Bits 2:1 Interrupt ID Bits ID0 and ID1These two bits are used to identify the highest-priority interrupt as shown in Table 28.  
Interrupt PendingThis bit indicates when a modem interrupt is pending. Whenever this bit is equal to 0, then one  
or more interrupts are pending. Whenever this bit is equal to 1, then no interrupts are pending. When an interrupt has  
occurred, the host can determine the cause of the interrupt by looking at the IIR interrupt ID bits 0 and 1 (and interrupt  
Bit 0  
ID bit 2 for FIFO mode).  
9.2.8  
Interrupt Enable Register (IER)  
Figure 21. Interrupt Enable Register (IER)  
0
0
0
0
MSIE  
RLSIE THREIE  
RDAIE  
Register 1  
(DLAB = 0)  
This register is used to enable up to five types of UART interrupts: receiver line status, received  
data available, character time-out indication (FIFO mode only), Transmitter Holding register  
empty, and modem status. Each enabled interrupt can individually cause an interrupt to host on the  
µP HINT output pin. To cause an interrupt to the host (HINT), both the interrupt enable bit and  
OUT2 (MCR2) must be set to 1.  
Bits 7:4 Not usedThese bits are permanently set to 0.  
Bit 3  
Bit 2  
MSIE (Modem Status Interrupt Enabled)when set to 1, this bit enables the modem status interrupt.  
RLSIE (Receiver Line Status Interrupt Enabled)when set to 1, this bit enables the receiver line status interrupt.  
THREIE (Transmitter Holding Register Empty Interrupt Enabled)when set to 1, this bit enables the Transmitter  
Holding register empty interrupt.  
Bit 1  
Bit 0  
RDAIE (Received Data Available Interrupt Enabled)when set to 1, this bit enables the received data available  
interrupt.  
9.2.9  
Transmitter Holding Register (THR)  
Figure 22. Transmitter Holding Register (THR)  
Register 0  
(DLAB = 0)  
THR  
The THR (Transmitter Holding register) is a write-only register used for sending data and AT  
commands to the modem.  
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9.2.10  
Receiver Buffer Register (RBR)  
Figure 23. Receiver Buffer Register (RBR)  
Register 0  
(DLAB = 0)  
RBR  
The RBR (Receiver Buffer register) is a read-only register used for receiving data and AT  
command responses from the modem.  
9.2.11  
Divisor Latch Registers (DLM and DLL)  
Figure 24. Divisor Latch Registers (DLM and DLL)  
Register 1  
DLM (MS)  
DLL (LS)  
(DLAB = 1)  
Register 0  
(DLAB = 1)  
The LS divisor latch (least-significant byte) and MS divisor latch (most-significant byte) are two  
read/write registers used to set the modem data rate. The data rate is selected by loading each  
divisor latch with the appropriate hex value. The programmable data rates are provided in the  
following table. For example, to use a data rate of 2400 bps, load a $00h into the DLM and a $30h  
into the DLL.  
Table 29. Programmable Data Rates  
Data Rate  
Divisor Number  
Divisor Latch (Hex)  
MS LS  
01 80  
(Decimal)  
300  
1200  
2400  
4800  
7200  
9600  
19200  
38400  
57600  
384  
96  
48  
24  
16  
12  
6
00  
00  
00  
00  
00  
00  
00  
00  
60  
30  
18  
10  
0C  
06  
03  
02  
3
2
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9.3  
16C550A UART FIFO Operation  
The modem 16C550A UART FIFO works in both interrupt and polled operation. A description of  
each type of operation is provided below.  
9.3.1  
FIFO Interrupt Mode Operation  
Both the modem receiver and transmitter UART FIFOs can be set up for interrupt mode operation.  
The RCVR FIFO trigger level and character time-out interrupts have the same priority as the  
current received data available interrupt. The XMIT FIFO empty interrupt has the same priority as  
the Transmitter Holding register empty interrupt. Information pertaining to using the receiver and  
transmitter FIFO interrupts is provided below.  
1. When both the receiver FIFO and the receiver interrupts are enabled (FCR0 = 1, IER0 = 1), the  
UART initiates RCVR interrupts under the following conditions:  
a. The receive data available interrupt (IIR = 04) is issued to the DTE when the FIFO has  
reached its programmed trigger level; the interrupt clears as soon as the FIFO drops below  
the programmed trigger level  
b. The data ready bit, DR (LSR0), is set as soon as a character is transferred from the  
Internal Shift register to the RCVR FIFO. DR is reset when the FIFO is empty.  
2. When the RCVR FIFO and receiver interrupts are enabled, the UART initiates a RCVR FIFO  
time-out interrupt under the following conditions:  
a. A RCVR FIFO time-out occurs when:  
At least one character is in the FIFO.  
The most recent serial character received was longer than four continuous character times  
ago.  
The most recent DTE read of the FIFO was longer than four continuous character times  
ago.  
b. When a time-out interrupt has occurred, then it is cleared and the timer is reset when the  
DTE reads one character from the RCVR FIFO.  
c. The time-out timer is reset after a new character is received or after the DTE reads the  
RCVR FIFO.  
3. When the transmitter FIFO and the transmitter interrupt are enabled (FCR0 = 1, IER1 = 1), the  
UART initiates XMIT interrupts under the following conditions:  
a. The Transmitter Holding register interrupt (IIR = 02) occurs when the XMIT FIFO is  
empty; it is cleared as soon as the transmitter holding register is written to or the IIR is  
read. During servicing, the 116 character interrupt can be written to the XMIT FIFO.  
9.3.2  
FIFO Polled Mode Operation  
Both the modem receiver and transmitter UART FIFOs can be set up for polled mode operation.  
The UART FIFO is set for polled mode when FIFOE (FCR0) = 1 and the respective interrupt  
enable bit (IER) = 0.  
In polling mode, the DTE checks the LSR for receiver and/or transmitter status. The LSR register  
provides the following information:  
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LSR7 indicates when any errors occur in the RCVR FIFO.  
TEMT indicates when both the XMIT FIFO and Shift registers are empty.  
The THRE bit (LSR5) is set to 1whenever the XMIT FIFO is empty.  
LSR1 through LSR4 specify when a break interrupt, framing error, parity error, or overrun  
error occurs.  
The DR bit (LSR0) is set to 1as long as there is at least one byte in the RCVR FIFO.  
Unlike FIFO interrupt mode, FIFO polled mode does not support buffer trigger levels or time-out  
conditions.  
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