'AT' Command Set Description

The modem (DCE) operates in either one of two states/modes: command or on-line. In both states, the data and commands _ including DCE responses _ are transferred through the UART Transmit Holding register (THR) and the Receiver Buffer register (RBR). Upon powering-up, the modem defaults to the command state. In the command state, the host (DTE) 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 CL-MD1414XX 'AT' command set and S-registers are divided into four categories: Group 3 fax, data, V.42/MNP and voice. Tables 1­2 through 1­7 provide summaries of all the commands, and Table 1­8 provides a summary of all the S-registers. All command lines sent to the modem, except for A/, must be preceded by an 'AT' and terminated by the contents of S-register S3 (typically a carriage return <CR>). An 'AT', which stands for 'attention', 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 that it 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. Fax 'AT' commands must have a semicolon (;) after the command if there are multiple fax commands on a line. The modem can be configured to send back (echo) to the DTE any data that the DTE sent to the modem (in command mode only). To repeat the last command, type A/ without using a carriage return. Four examples of 'AT' command strings are as follows:

ATS1?<CR>
A/
AT C1 D2 +FCLASS=? <CR>
AT C1 D2 +FCLASS=?; S0=1 %lt;CR>

The modem provides status information to the DTE in the form of response codes. These response codes can be selected to be in either text or numeric form. The supported response codes are provided in Tables 1­9 through 1­11. Five examples of modem responses are as follows:

OK
ERROR
CONNECT 2400
0
5

In the on-line state, the DCE is 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 on-line state, the DCE does not 'echo-back' any of the data that the DTE sent to the DCE. The modem will recognize 'AT' commands from the DTE at any valid data rate from 300 bps to 38,400 bps (i.e., the modem autobauds up to 38,400 bps for the serial host interface). Even though the modem will recognize commands at 38,400 bps, the DTE should use the specified data rate necessary for each mode. The data rates for each mode are as follows:

Data Mode
300 - 14,400 bps All direct mode data modes (\N1)
300 - 57,600 bps Parallel and PCMCIA host Interfaces: All data modes (\Nn) except direct mode (\N1)
300 - 38,400 bps Serial host interface: All data modes (\Nn) except direct mode (\N1)
Fax Mode
19,200 bps 'AT' commands and data transfers
Voice Mode
19,200 bps 'AT' commands
19,200 - 57,600 bps Playback and record modes (varies according to compression type).

Basic Data Modem 'AT' Commands

Command Default Function
* Value saved in NVRAM.
** Command not preceded by an 'AT'.
_ Patent pending.
A/ ** none Repeat last command
A none Answer
Bn * 1 Select CCITT or Bell
Cn 1 Carrier control option
D none Dial command
En * 1 Command echo
Fn 1 On-line echo
Hn 0 Switch hook control
In 0 Identification/checksum
Kn none SRAM buffer control
Ln * 2 Speaker volume control
Mn * 1 Speaker control
Nn * 1 Connection data rate control
On 0 Go on line
P * none Select pulse dialing
Qn * 0 Result code display control
Sn none Select an S-register
Sn=x none Write to an S-register
Sn? none Read from an S-register
? none Read last accessed S-register
T * none Select DTMF dialing
Vn * 1 Result code form
Xn * 4 Result code type
Yn * 0 Long space disconnect
Zn 0 Recall stored profile
&Cn * 1 DCD option
&Dn * 2 DTR option
&F none Load factory defaults
&Gn * 0 Guard tone option
&Jn * 0 Auxiliary relay control
&M0 * 0 Communication mode option
&Pn * 0 Dial pulse ratio
&Q0 * 0 Communication mode option
&Sn * 0 DSR option
&Tn 0 Self test commands
&Vn 0 View active and stored configuration
&Un * 0 Disable Trellis coding
&Wn 0 Stored active profile
&Yn * 0 Select stored profile on power up
&Zn=x none Store telephone number
%En * 1 Auto-retrain control
%G0 * 0 Rate Renegotiation
%Q none Line signal quality
-Cn * 0 Generate data modem calling tone

Fax Identity and Test 'AT' Commands

Command Function
+FMFR? Identify modem manufacturer
+FMDL? Identify product model
+FREV? Identify product revision
+FTTn Fax transmit test command
+FRTn Fax receive test command

Data/Fax Class 1 'AT' Commands

Command Function
+FCLASS? Mode query
+FCLASS=n Fax mode selection
+FCLASS=? Supported modes
+FRH= Receive HDLC data
+FRM= Receive data
+FRS= Wait for Silence
+FTH= Transmit HDLC data
+FTM= Transmit data
+FTS= Stop transmission and pause

Voice Mode 'AT' Commands

Command Default Function
* Value saved in NVRAM.
#VBP none Generate beep tone
#VCL=n 0 Voice mode selection
#VCSD=n 0 Command mode silence detection
#VGPS=n * 0 Input pin function selection
#VGPC=n * 0 Input pin character selection
#VIN none Read general-purpose input pins
#VIP=n 0 Initialize parameter
#VLN=n 0 Relay/speaker control
#VOUT=n 0 Write to output pins
#VPH none Telephone-emulation mode1
#VPL=n 127 Play level
#VPY none Play mode
#VRD none Record mode
#VRL=n 127 Record level
#VSL=n 127 Record silence threshold level
#VSM=n CL1 Sampling mode
#VSQT=n 0 Record 'q' silence time
#VSR=n 9600 Sampling rate
#VSST=n 60 Record 's' silence time

V.42, MNP 'AT' Commands

Command Default Function
* Value saved in NVRAM.
%An * 13 Set auto-reliable fallback character
%Cn * 1 MNP 5 data compression control
\An * 3 MNP block size
\Bn * none Transmit break
\Cn * 0 Set auto-reliable buffer
\Gn * 0 Set modem port flow control
\Jn * 0 Bps rate adjust control
\Kn * 5 Set break control
\Nn * 3 Set operating mode
\O none Originate reliable link
\Qn * 3 Set serial port flow control
\Tn * 0 Set inactivity timer
\U none Accept reliable link
\Vn * 2 Modify result code form
\Xn * 0 Set XON/XOFF pass-through
\Y none Switch to reliable mode
\Z none Switch to normal mode
-Jn * 1 Set V.42 detect phase
"Hn * 3 V.42 bis compression control
"On 16 V.42 bis string length

Dial Modifiers

Command Function
0 to 9 Dialing digits
A, B, C, D, *, # Tone dial characters
P Pulse dial
R Reverse originate mode
S=n Dial NVRAM telephone number
T Tone dial
W Wait for dial tone
, Pause
! Flash hook
@ Wait for quiet answer
; Return to idle state
- ( ) Ignored by modem

Basic Response Codes (\V0)

Numeric Code Verbose Code
0 OK
1 CONNECT
2 RING
3 NO CARRIER
4 ERROR
5 CONNECT 1200
6 NO DIAL TONE
7 BUSY
8 NO ANSWER
10 CONNECT 2400
11 CONNECT 4800
12 CONNECT 7200
14 CONNECT 9600
16 CONNECT 12000
17 CONNECT 14400
+F4 +FCERROR

Modified Response Codes (\V1)

Numeric Code Verbose Code
22 CONNECT 300/REL
24 CONNECT 1200/REL
25 CONNECT 2400/REL
26 CONNECT 4800/REL
27 CONNECT 7200/REL
28 CONNECT 9600/REL
29 CONNECT 12000/REL
30 CONNECT 14400/REL

V.42 Extended Response Codes (\V2)

Numeric Code Verbose Code
32 CONNECT 300/REL-MNP
34 CONNECT 1200/REL-MNP
35 CONNECT 2400/REL-MNP
36 CONNECT 4800/REL-MNP
37 CONNECT 7200/REL-MNP
38 CONNECT 9600/REL-MNP
39 CONNECT 12000/REL-MNP
40 CONNECT 14400/REL-MNP
42 CONNECT 300/REL-MNP-5
44 CONNECT 1200/REL-MNP-5
45 CONNECT 2400/REL-MNP-5
46 CONNECT 4800/REL-MNP-5
47 CONNECT 7200/REL-MNP-5
48 CONNECT 9600/REL-MNP-5
49 CONNECT 12000/REL-MNP-5
50 CONNECT 14400/REL-MNP-5
54 CONNECT 1200/REL-LAPM
55 CONNECT 2400/REL-LAPM
56 CONNECT 4800/REL-LAPM
57 CONNECT 7200/REL-LAPM
58 CONNECT 9600/REL-LAPM
59 CONNECT 12000/REL-LAPM
60 CONNECT 14400/REL-LAPM
64 CONNECT 1200/REL-LAPM-V.42BIS
65 CONNECT 2400/REL-LAPM-V.42BIS
66 CONNECT 4800/REL-LAPM-V.42BIS
67 CONNECT 7200/REL-LAPM-V.42BIS
68 CONNECT 9600/REL-LAPM-V.42BIS
69 CONNECT 12000/REL-LAPM-V.42BIS
70 CONNECT 14400/REL-LAPM-V.42BIS

Basic Data Mode 'AT' Command Set Summary

Command Default Description
NOTE: An asterisk (*) denotes the factory-default setting.
A/ none Repeat Last Command: This command re-executes the last 'AT' command string stored in the command buffer. The A/ command is the only command not preceded by 'AT' and ended by a carriage return.
A none 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.
Bn 1 Select CCITT or Bell: This command selects whether the modem is configured as a CCITT or BELL modem.
n = 0 Selects CCITT V.22 when the modem is at 1200 bps.
n = 1 Selects Bell, 212A when the modem is at 1200 bps,
and Bell 103J when the modem is at 300 bps. *
Cn 1 Carrier Control Option: This command is reserved for selecting between controlled carrier or constant carrier modes. This modem supports only constant carrier mode.
n = 0 Transmit carrier always off (returns an ERROR message)
n = 1 Normal transmit carrier *
D none 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

0 to 9 Dialing Digits
A, B, C, D, *, # Tone Dial Characters
P Pulse Dial _ Configures the modem to use pulse dialing to dial a telephone number.
R Reverse Originate Mode _ Places the modem in answer mode. This modifier should be the last character in the dialing string (e.g., ATDT 123-45678R)
S = n Dial NVRAM Telephone Number _ Causes the modem to dial a telephone number previously stored in the NVRAM with the AT&Zn = x command.
T Tone Dial _ Configures the modem to use DTMF tones to dial a telephone number.
W Wait for Dial Tone _ Causes 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 will then process the next command in the dial string. If a busy signal is detected, the modem will respond back to the DTE with a busy response code, and then go into off-line command mode.
, Pause _ Causes the modem to pause or delay implementing the next parameter in the dial string by the time specified in S-register S8.
! Flash Hook _ Causes the modem to go on-hook for 0.75 seconds.
@ Wait for Quiet Answer _ Causes 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 State _ Causes the modem to enter on-line command mode without initiating a data modem handshake (used for phone directory auto-dialers).
- ( ) Ignored by Modem _ These four characters are ignored by the modem, but space may be included in the dial string for separating area codes and numbers.
En 1 Command Mode Echo: This command selects whether the modem echoes 'AT' commands back to the host in either on-line or off-line command mode.
n = 0 Echo disabled
n = 1 Echo enabled *
Fn 1 On-line Echo: This command is normally used to select whether the modem echoes data back to the host during on-line data mode. This device set does not support on-line data mode echo.
n = 0 Echo enabled (returns an error message)
n = 1 Echo disabled *
Hn 0 Switch Hook Control: This command is used to control the telephone line relay (OHREL*) and causes the modem to either hang-up or pick-up the telephone line.
n = 0 Hang-up telephone line (go on-hook)
n = 1 Pick-up telephone line (go off-hook)
In 0 Identification/Checksum Option: This command causes the modem to send product code and hardware setup information to the DTE.
n = 0 Report product code *
n = 1 Firmware version #
n = 2 Verify ROM checksum
n = 3 Device set name
n = 4 Modem configuration
Bit 0 0 = Hayes Escape Sequence
1 = TIES Escape Sequence
Bit 1 0 = Data/fax/voice without V.42/MNP firmware
1 = Data/fax/voice with V.42/MNP firmware
Bit 2 0 = Serial host interface
1 = Parallel host interface
Bit 3 0 = No external Static RAM present
1 = External Static RAM present
Bit 4 0 = 8K x 8 static RAM present (valid only if bit 3 = 1)
1 = 32K x 8 static RAM present (valid only if bit 3 = 1)
Bits 5-7 Reserved

ATI
1.04

OK

ATI1
HD54-HM48-HEC09

OK

AT2
OK

OK

ATI3
CL-MD1414AT/EC

OK

ATI4
31 --Decimal 31 (hex 1F) Indicates TIES
Escape Sequence, V.42/MNP firmware
present,
OK parallel host interface and a 32K SRAM
Kn 1 Buffer Control: This command selects whether the modem SRAM is used for voice and fax mode.
n = 0 SRAM buffer disabled (default when no SRAM is available)
n = 1 SRAM buffer enabled (default when the SRAM is available on modem board)*
Ln 2 Speaker Volume Control: This command selects the modem speaker volume.
n = 0 Low speaker volume
n = 1 Low speaker volume
n = 2 Medium speaker volume *
n = 3 High speaker volume
Mn 1 Speaker Control: This command specifies when the speaker is turned on and off.
n = 0 Speaker always off
n = 1 Speaker on until carrier present *
n = 2 Speaker always on
n = 3 Speaker off during dialing, and on until carrier
Nn 1 Select Data Rate Handshake: This command specifies whether the resulting modem-to-modem data rate can be different than the local DTE-to-modem data rate.
n = 0 When originating or answering, handshake only at the DTE-to-modem data rate.
n = 1 When originating or answering, begin handshaking at the DTE-to-modem data rate. If the remote modem does not support the local DTE-to-modem data rate, fall down to the highest compatible data rate. *
On 0 Go On-line: This command causes the modem to return back to on-line data mode from on-line command mode.
n = 0 Returns the modem to data mode. *
n = 1 Begins an equalizer retrain sequence, then returns to data mode. This parameter is only valid for 2400-bps connections.
P none Select Pulse Dialing: This command configures the modem to use pulse dialing next time the modem dials a telephone number.
Qn 0 Result Code Display Control: This command selects whether the modem will send result codes to the DTE.
n = 0 Result codes enabled *
n = 1 Result codes disabled
Sn none Select an S-Register: This command is used to select the current S-register.
Range: 0-30
Sn=x none Write to an S-Register: This command is used to write a decimal number 'x' to S-register 'n'.
n = 0-30
x = 0-255
Sn? none Read an S-Register: This command is used to read a decimal number from S-register 'n'.
n = 0-30
T none Select Tone Dialing: This command configures the modem to use DTMF tones next time the modem dials a telephone number.
Vn 1 Result Code Form: This command selects whether modem response codes are in either numeric or verbose form.
n = 0 Numeric form.
n = 1 Verbose (text) form. *
Xn 4 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 Result codes 0: 4 enabled. Busy and dial tone detect disabled.
n = 1 Result codes 0: 5, 10 enabled. Busy and dial tone detect disabled.
n = 2 Result codes 0: 6, 10 enabled. Busy detect disabled and dial tone detect enabled.
n = 3 Result codes 0: 5, 7, 10 enabled. Busy detect enabled and dial tone detect disabled.
n = 4 Result codes 0: 7, 10 enabled. Busy and dial tone detect enabled. *
Yn 0 Long Space Disconnect: This command controls whether the modem will send silence to the remote modem before disconnecting and disconnect after seeing 1.6 seconds of silence from the remote modem.
n = 0 Disables long space disconnect *
n = 1 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 will send at least 4 seconds of silence before hanging up.
Zn 0 Reset Modem/ Recall Stored Profile: This command causes the modem to go on-hook (hang-up), perform a warm reset, and then 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 all subsequent commands are ignored.
n = 0 Resets the modem and recalls user profile 0 *
n = 1 Resets the modem and recalls user profile 1
&Cn 1 Data Carrier Detect (DCD) Option: This command controls how the modem functions in relation to the DCD or RLSD signal.
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.*
&Dn 2 Data Terminal Ready (DTR) 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 as the modem does not send an 'OK' message to indicate it has performed the requested function.
n = 0 In asynchronous mode (&Q0), the modem ignores DTR.
n = 1 The modem switches from data mode to command mode when an on-to-off transition of DTR occurs.
n = 2 An on-to-off transition of DTR causes the modem to go on-hook (hang-up) and disable auto-answer mode. Auto-answer mode (S0 is not equal to zero) is enabled when DTR is turned on. *
n = 3 An on-to-off transition of DTR re-initializes the modem. The re-initialize procedure performs a power-up reset, except that the UART registers are not re-configured. Note: The modem will not respond to a DTR toggle in sleep or power down mode (see S-register S30). It is recommended that a character be sent to wake up the modem prior to toggling DTR .
&F none Load Factory Defaults: This command loads command and S- register factory defaults into the active configuration, and configures the modem for data mode.
&Gn 0 Guard Tone Option: This command controls whether the modem will send out guard tones while connected to a remote modem. 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.
n = 0 Guard tone disabled. *
n = 1 550-Hz guard tone enabled.
n = 2 1800-Hz guard tone enabled.
&Jn 0 Auxiliary Relay Control: This command controls whether the modem supports the A/A1 function. A/A1 is used only for RJ-12 and RJ-13 telephone connectors, and is not used for RJ-11 telephone connectors. A and A1 are two pins on the RJ-13 connector that are used to indicate when a modem/telephone is being used on a multi-line telephone system. To implement the A/A1 feature, the device set provides an A/A1* relay driver. Typically, the A/A1* relay driver drives a normally-open relay that connects the A and A1 signals from the RJ-13 telephone connector together _ pins 2 and 5 respectively. When enabled (&J1), the modem activates the A/A1* relay driver whenever it goes off-hook. Activating the A/A1* relay driver causes the normally- open relay to close and short A and A1 together. Caution: The A/A1 function should never be used on an RJ-11 telephone jack, since most homes provide a second telephone signal on RJ-11 pins 2 and 5. Additionally, problems may occur if &J1 is selected, and the A/A1* relay driver is used to control other modem circuitry (refer to AT#VLN=n command). Thus, it is recommended that &J0 always be used.
n = 0 Auxiliary relay is never operated. *
n = 1 A lead is connected to the A1 lead while the modem is off-hook.
&P 0 Dial Pulse Ratio: This command determines the make/break (i.e., off-hook/on-hook) ratio during pulse dialing.
n = 0 Make = 39%; Break = 61% for use in the United States. *
n = 1 Make = 33%; Break = 67% for use in the United Kingdom and Hong Kong.
&Sn 0 Data Set Ready (DSR) Option: This command controls how the modem treats the DSR signal.
n = 0 DSR circuit always on *
n = 1 DSR circuit is on during handshaking, off in test or idle modes. DSR is on when carrier is lost.
&Tn 0 Self-test Command: This command is used to initiate and terminate loopback tests for testing modem-to-modem and DTE-to-modem data communication integrity.
n = 0 Terminates test in progress *
n = 1 Local analog loopback
n = 3 Local digital loopback
n = 4 Grants RDL request from remote modem
n = 5 Denies RDL request from remote modem
n = 6 Remote digital loopback
n = 7 Remote digital loopback with self-test
n = 8 Local analog loopback with self-test
&U 0 Disable Trellis coding: This command selects whether the modem will transmit and receive modulated 9600 bps carrier with QAM or Trellis encoding for V.32. Range: n = 0-1
n = 0 Enabled (Trellis modulation with QAM modulation as a fallback)*
n = 1 Disabled (QAM modulation only)
&Vn 0 View Active Configuration and Stored Profiles: This command causes the modem to send command and S-register configuration information to the DTE for the following: the active user profile, and one of two stored user profiles.
n = 0 Stored profile 0 *
n = 1 Stored profile 1

AT&V1

Active Profile:
+FCLASS=0 #VCL=0 #VLN=25
B1 E1 L2 M1 N1 P Q0 V1 X4 Y0 &C1 &D2 &G0 &J0 &P0 &Q0 &S0 &Y0 -C0 %E1 %G0
\A3 \C0 \G0 \J0 \K5 \N3 \T00 \V2 \X0 %A013 %C1 -J1 "H3 "O016
S00:000 S01:000 S02:043 S03:013 S04:010 S05:008 S06:002 S07: 060 S08:002
S09:006 S10:014 S11:095 S12:050 S14:170 S16:000 S18:000 S21:048 S22:118
S23:021 S25:005 S26:001 S27:064 S30:010 S37:000 S90:000 S108:002 S109:062

Stored Profile 1:
B1 E1 L2 M1 N1 P Q0 V1 X4 Y0 &C1 &D2 &G0 &J0 &P0 &Q0 &R0 &S0 &X0
\A3 \C0 \G0 \J0 \K5 \N3 \T00 \V2 \X0 %A013 %C1 -J1 "H3 "O016
S00:000 S06:002 S07: 060 S08:002 S09:006 S10:014 S11:095 S12:050 S14:170
S16:000 S18:000 S21:048 S22:118 S23:021 S25:005 S26:001 S27:064 S30:010
S37:000 S90:000 S108:002 S109:062

Telephone Numbers:
&Z0 12345
&Z1 T4444444
&Z2 T12345
&Z3 T 1 (123) 456-7890
&Wn 0 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'.
n = 0 Store in user profile 0 *
n = 1 Store in user profile 1
&Yn 0 Select Stored Profile on Power-up: This command selects the particular stored user profile from the NVRAM that will be loaded into the active profile upon modem power up.
n = 0 Select profile 0 *
n = 1 Select profile 1
&Zn=x none Store Telephone Number: This command stores up to a 38-digit telephone number in to the NVRAM. To dial the stored telephone, use the ATDS=n command.
x = 0, 9, A, B, C, D, #, *, T, P, R, W, @, ,,!,;
n = 0-3
-Cn 0 Generate Data Modem Calling Tone: This command allows the DTE to select whether the modem will send 1300 Hz calling tone when originating a Data Modem connection.
n = 0 Calling tone disabled *
n = 1 Calling tone enabled
%En 1 Auto-retrain Control (V.22 bis and V.32 bis only): This command controls whether the modem will automatically initiate a modem retrain whenever the Received Data signal quality falls below a threshold that may affect data reliability. The value for 'n' is stored in the NVRAM, but it is not displayed by the 'AT&Vn' command.
n = 0 Disabled*
n = 1 Enabled
%Gn 0 Auto Fallforward/fallback Enable (V.32 bis only): This command selects whether the modem will automatically initiate a change to a higher speed or lower speed depending on received signal quality (i.e. Rate Negotiation). The modem always responds to any rate change initiated by the remote modem.
n = 0 Disabled *
n = 1 Enabled
%Q none Line Signal Quality: This command returns the higher order byte of the EQM value. This information indicates the quality of the telephone line signal. Note that this value will be different for different DAAs.
Range: 0-255
0 - 7 No Retrain
8 - 255 Modem performs a Retrain (i.e., if configured for %E1)

Data Mode Error Correction and Data Compression

The CL-MD1414XX supports two types of error correction (MNP 2-4 and V.42) and data compression (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.42 bis data compression requires V.42 (LAPM only). MNP 5 requires MNP 2-4. The supported V.42/MNP 'AT' command set is listed below.

V.42, MNP 'AT' Commands

Five operating modes, selectable by the \Nn command, are supported to allow the DCE to communicate with remote modems that may or may not support error correction and data compression. The five operating modes are Normal, Direct, MNP Reliable, V.42 Auto-reliable and V.42 Reliable. Speed buffering, which is used for all operating modes except \N1, allows the DTE-to-modem data rate to be different than 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 except direct mode (\N1), the DTE-to-modem data rate can be set for any valid speed between 300 bps to 38,400 bps (i.e., the modem autobauds up to 38,400 bps in the serial host interface and up to 57,600 bps in the parallel and PCMCIA host interfaces). In direct mode, the DTE-to-modem data rate can only be set to 300, 1200, 2400, 4800, 7200, 9600, 12000, and 14400 bps. Each operating mode is explained in more detail on the following page.

Normal Mode (\N0) No error correction/data compression, but speed buffering is supported.
Direct Mode (\N1) No error correction/data compression or speed buffering.
MNP Reliable Mode (\N2) MNP 2-5 connection only. The modem hangs up if an MNP connection cannot be established.
V.42 Auto-Reliable Mode (\N3) V.42/V.42 bis with fallback to MNP 2-5 or normal mode.
V.42 Reliable Mode (\N4) V.42, V.42 bis or MNP 2-5 only connection. The modem hangs up if a V.42/V.42bis/MNP 2-5 connection cannot be established.

Connection types corresponding to \Nn settings

NOTES:
  • MNP 5 requires that the modem be configured for %C1.
  • V.42 bis requires that the modem be configured for "H3.
  • Refer to \Cn and %A commands for more information about auto-reliable mode.
The list of commands needed to enter a specific error correction or data compression mode are provided below:
Direct mode only: &F \N1 or
\N1
V.42 bis with fallback to MNP 5: &F \N3 or
\N3 "H3 %C1
MNP 2-4 or V.42:
V.42 bis with fallback to V.42/MNP 2-4: &F \N4 %C0 or
\N4 %C0 "H3 -J1
V.42 bis only: &F \N4 -J0 or
\N4 -J0 "H3
V.42 only: &F \N4 -J0 "H0 or
\N4 -J0 "H0
MNP 5 with fallback to MNP 2-4: &F \N2 or
\N2 %C1
MNP 2-4 only: &F \N2 %C0 or
\N2 %C0

V.42 and MNP Data Mode 'AT' Command Set Summary

Command Default Description
NOTE: An asterisk (*) denotes the factory-default setting.
%An 13 Set Auto-reliable Fallback Character: In auto-reliable mode (\N3), with auto-reliable fallback character enabled (\C2), receipt of the fallback character from the line during the V.42 detection phase will cause the modem to switch to 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.
n = 0-127 (ASCII character)
%Cn 1 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%.
n = 0 No compression
n = 1 MNP Class 5 compression *
\An 3 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.
n = 0 Maximum 64 characters
n = 1 Maximum 128 characters
n = 2 Maximum 192 characters
n = 3 Maximum 256 characters *
\Bn none Transmit Break: This command causes the modem to send a break (Attention signal), for a duration specified by 'n', to the remote modem. When n = 0, the default break length is used.
n = 0-9 Break length in 100 msec
\Cn 0 Set Auto-reliable Buffer (requires a license from Microcom,): In auto-reliable mode (\N3), 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.
n = 0 Does not buffer data. *
n = 1 Buffers data for four seconds until 200 characters have been buffered or SYN character is detected, then switches to reliable mode. If the buffer fills, data is passed to the serial port.
n = 2 Does not buffer data. Switches to normal mode upon receipt of auto-reliable fallback character and passes it to serial port. This feature is used to allow non-V.42 modems to connect immediately to a V.42 modem without data loss.
\Gn 0 Set Modem Port Flow Control: In normal mode (\N0 or after fallback), this command enables modem-to-modem flow control using XOFF (13 hex) and XON (11 hex) characters to stop and start transmission between modems, respectively.
n = 0 Disables port flow control *
n = 1 Sets port flow control to XON/XOFF
\Jn 0 BPS Rate Adjust Control: If enabled, the serial-port speed will automatically be changed to the modem-connection speed, forcing the user to change the bps rate of the DTE-to-modem, if needed. If disabled, the serial-port speed is independent of the connection speed, which allows much greater throughput when using error correction and data compression.
n = 0 Turns off feature *
n = 1 Turns on feature
\Kn 5 Set Break Control: Defines what action the modem takes when a break (Attention signal) is sent or received, as described below.
In Connect State, if reliable mode then transmit break to remote:
n = 0,2,4 Enter command state, but do not send a break.
n = 1 Destructive/expedited
n = 3 Non-destructive/expedited
n = 5 Non-destructive/non-expedited
In Command State, if reliable mode then transmit break to remote:
n = 0,1 Destructive/expedited
n = 2,3 Non-destructive/expedited
n = 4,5 Non-destructive/non-expedited
In Connect State, if direct mode then receive break at serial port:
n = 0,2,4 Immediately send break and enter command state.
n = 1,3,5 Immediately send break through
In Connect State, receive break at modem port, send to serial port:
n = 0,1 Destructive/expedited
n = 2,3 Non-destructive/expedited
n = 4,5 Non-destructive/non-expedited
Default: 5
\Nn 3 Set Operating Mode: Determines the type of connection attempted by the modem.
n = 0 Normal Mode _ No data compression or error correction, but uses speed buffering.
n = 1 Direct Mode _ No data compression, error correction, or speed buffering.
n = 2 MNP Reliable Mode _ The modem attempts to negotiate an MNP error-correction 'reliable' link, hanging up if it fails.
n = 3 V.42 Auto-reliable Mode * _ If V.42 detection is enabled (-Jn), a LAPM or MNP link can be detected and negotiated, otherwise only LAPM will be attempted. If configured for -J0 and a protocol connection is not made, the modem will hang up. If configured for -J1 and a protocol connection is not made, the modem will fall back to speed buffering mode.
n = 4 V.42 Reliable _ The modem attempts to negotiate LAPM error correction, hanging up if it fails.
NOTE: 300 bps does not support synchronous operation. The mode will automatically fall back to MNP asynchronous operation.
\O none Originate Reliable Link: In normal mode (\N0), the modem will attempt to originate an MNP link, regardless of whether the modem originated or answered the telephone call (physical connection). The remote modem must answer the MNP link request for the link to be established (refer to the \U command).
\Qn 3 Set Serial Port Flow Control: This command specifies the DTE-to- modem flow control. Software flow control uses the XOFF (13 hex) and XON (11 hex) characters to stop and start data transmission, respectively, both to and from the DTE. Unidirectional hardware flow control uses the CTS control line to stop/start data from the DTE only, while bidirectional hardware flow control also uses the RTS control to stop/start data from the modem.
n = 0 Disables flow control
n = 1 XON/XOFF software flow control
n = 2 Unidirectional hardware flow control
n = 3 Bidirectional hardware flow control *
\Tn 0 Set Inactivity Timer: During a normal or reliable connection, if no data is sent or received within the inactivity time period, the link will be disconnected. The default of zero disables this feature.
n = 0-90 Length in minutes
n = 0 Disables inactivity timer
\U none Accept Auto-reliable Link: In normal mode (\N0), the modem attempts to answer an MNP link request, regardless of whether the modem originated or answered the telephone call (physical connection). The remote modem must originate the MNP link request for the link to be established (refer to the '\O' command).
\Vn 0 Modify Result Code Form: This command specifies which modem response codes are supported.
n = 0 Enables codes defined by ATV command (see Table 1­9)
n = 1 Enables modified MNP codes (see Table 1­10)
n = 2 Enables extended V.42 codes * (see Table 1­11)
\Xn 0 Set XON/XOFF Passthrough: If software flow control is enabled (\Q1), this command defines whether the XON (11 hex) and XOFF (13 hex) 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.
n = 0 Processes flow control characters *
n = 1 Processes flow control characters and passes them through
to the local or remote so they can process the characters.
\Y none Switch to Reliable Mode: In normal mode (\N0), the modem attempts to originate or answer an MNP link request, depending on whether the modem originated or answered the physical connection, respectively. The remote modem must attempt to answer/originate the MNP link for the link to be established.
\Z none Switch to Normal Mode: During an MNP link, the modem will disconnect the link (exit error correction/data compression) and change to normal mode, without disconnecting the modem-to-modem connection.
-Jn 1 Set V.42 Detect Phase: In V.42 modes (\N3, \N4), this command specifies whether the modem will detect V.42, MNP, or no error-correcting protocols from the remote modem and change to the appropriate mode. Otherwise, only LAPM will be attempted.
n = 0 Disables the V.42 detect phase
n = 1 Enables the V.42 detect phase *
"Hn 3 V.42 bis Compression Control: This command specifies whether the data in the LAPM frames are compressed using the V.42 bis data compression, which can improve throughput by as much as 400%. Compression can be negotiated to operate in only one direction, or in both directions.
n = 0 Disables V.42 bis
n = 1 Enables V.42 bis only when transmitting data
n = 2 Enables V.42 bis only when receiving data
n = 3 Enables V.42 bis for both transmitting and receiving data *
"On 16 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 16 optimizes throughput for most file types.
n = 6-250 = Number of characters

Fax Mode 'AT' Commands

The CL-MD1414XX implements 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 CL-MD1414XX-based modem to communicate with Group 3 fax machines. In addition, these device sets provide fax identity and test commands. A description of each fax 'AT' command is provided in Table 1-17. This Programmer's Guide should be used with the EIA/TIA-578, CCITT T.30 and T.4 specifications, and Class 1 Fax Application Note. The Cirrus Logic Class 1 Fax Application Note shows several examples of using the fax 'AT' commands, and how to originate and answer a fax call.

The fax identity commands are AT+FMFR?, AT+FMDL? and AT+FREV?. These commands respond back with modem manufacturer, product model, and product revision information, respectively.

The test commands AT+FTTn and AT+FRTn allow the modem manufacturer to test the fax transmit and receive modes during manufacturing testing.

The fax Class 1 'AT' commands are divided into three types: class selection and capabilities, data stream transfers, and silence-time timers. All commands, except the silence-time timers, must be the last command on the command line.

Fax Class 1 and Test 'AT' Commands

Each command may be used as follows:

+F? read current setting
+F = ? read permissible settings
+F = set parameter

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 38,400 bps (see Section 1.1). In Class 1, it is recommended that the DTE-to-modem data rate be set to 19,200 bps. The silence-time timers consist of AT+FTS = <TIME> and AT+FRS = <TIME>. Silence time is defined as the amount of time that the modem neither receives nor transmits any energy (i.e., 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 supported values for <MOD> are provided in the following table.

During data transfer, an ASCII character (hex $10) 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 ..... end of data stream
any data ..... single $10 in data stream
any data ..... delete both 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 which is equipped with an SRAM, will buffer up to 1.7 seconds 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, then the data will be transmitted immediately to the remote modem without waiting for the buffer to fill up.

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 must also recognize <DLE> <ETX> as the stream terminator. Upon detecting a <DLE> <DLE>, the DTE must reinsert a single <DLE> in its place. A modem equipped with an SRAM ( 8K) will buffer up to 1.7 seconds of facsimile 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 by using HDLC formatting. The format for HDLC framing is provided below. When sending the HDLC data, the modem automatically generates the flags, and generates or checks the Frame Checking Sequence (Frame Check Sum). All the other fields are transmitted to or received from the DTE (i.e., these fields are under the control of the DTE).

After receiving a frame correctly using the AT+FRH command (FCS is OK), the DCE will return an 'OK' message to the DTE. If the frame is received in error (FCS is not OK, carrier lost, or data lost due to data overflow), the DCE will return an 'ERROR' message to the DTE; the DTE should discard the frame. NOTE: If the telephone line is on-hook, the modem will respond back to the DTE with an 'ERROR' message whenever any of the fax 'AT' commands, except +FCLASS command, are sent to the modem.

Like 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 data modem mode, the modem does not support auto-answering while in fax mode. It is recommended that S-register S0 be set to a '0' (i.e., use 'ATA') whenever the modem is expected to receive a fax call.

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), looks for 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 will then send a 'CONNECT' message followed by the Class 1 HDLC frame information to the DTE. If the HDLC flags are not detected within the time limit defined by S-register S7, the modem will send a 'NO CARRIER' message to the DTE and then hang up the line. If the modem hangs up the line during processing the ATD command (i.e., the modem is on-hook), the modem will respond back with an 'ERROR' message anytime 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 answer tone followed by HDLC flags. The modem then sends a 'CONNECT' message 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 answer tone;
  3. It causes the modem to act like 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: #VCL

Fax Mode 'AT' Command Set Summary

Command Default Description
NOTE: An asterisk (*) denotes the factory-default setting.
+FCLASS none 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 only valid 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 'OK' message at the same DTE-to-modem data rate that this command was issued.
Range: n = 0, 1
n = 0 Configures DCE for data modem operation
n = 1 Configures DCE for fax modem operation
+FMFR? none Identify Modem Manufacturer: This command causes the DCE to send a message to the DTE indicating the DCE manufacturer.
AT+FMFR?
CIRRUS LOGIC

OK
+FREV? none Identify Product Revision: This command causes the DCE to report the modem device set revision level. This command is identical to 'ATI1'.
AT+FREV?
HD54-HM48-HEC09

OK
+FMDL? none Identify Product Model: This command causes the DCE to report the modem device set name. This command is identical to 'ATI3'.
AT+FMDL?
CL-MD1414XX

OK
NOTE: The modem responds with 'CL-MD1414XX' for all device sets that support V.42/MNP protocols.
+FRH none Receive HDLC Data: The +FRH = command causes the modem to receive HDLC framed data using the modulation mode selected in , and delivers the next received frame to the DTE.
If the modem detects the selected carrier signal with an HDLC flag, the modem will send a 'CONNECT' result code to the DTE. If a different signal is detected, the modem will send the '+FCERROR' (Connect Error) result code to the DTE, and returns to command mode. Additionally, the modem will return to command mode upon loss of carrier, and send a 'NO CARRIER' result code to the DTE. After receiving the HDLC flags, the modem will strip flags, and buffers the received frames. The received data, starting with the first non-flag byte and continuing through the last FCS byte will be transferred to the DTE. The DTE should ignore the value of the FCS bytes. Additionally, the modem performs HDLC zero-bit deletion and error checking.
After the FCS bytes are transferred, the modem will mark the end of the frame with , and report the status of the frame reception to the DTE. If the frame was received correctly (FCS is OK), the modem will return a 'OK' result code. If the frame was received in error (FCS is not OK, or carrier lost, or data lost due to data overflow), the DCE will return an 'ERROR' result code; the DTE should discard this frame.
After sending the status result code, the modem is ready to accept new commands from the DTE.
The modem will obey 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 will enter command mode and return an 'OK' result code.
After sending the result code indicating that frame reception is complete, the modem will continue to receive and buffer data in the selected mode. If the DTE issues another +FRH = command, the modem will return another 'CONNECT' result code and continue with HDLC reception. If the DTE issues any command that changes modulation, the DCE will stop the receive process; any buffered data will be discarded and the command will be processed.
NOTE: If the modem is on-hook, then the modem will always return an 'ERROR' message to the DTE after receiving the +FRH = command.
Range: = 3
(Refer to the Selection Table.)
+FRM none Receive Data: The +FRM = command causes the modem to enter receive mode using the modulation scheme specified in the . may have the values shown in the Selection Table.
When the selected carrier is detected, the modem will send a 'CONNECT' result to the DTE. If a different signal is detected, the modem will send a '+FCERROR' (connect error) result code to the DTE, and return to command mode.
After receiving the selected carrier, the modem will transfer all received data patterns to the DTE as consecutive start-stop framed bytes, including leading Marking conditions or flags. The modem will mark the end of the data stream with a .
The modem will return to command state upon loss of carrier, and send a 'NO CARRIER' result code to the DTE.
NOTE: If the modem is on-hook, then the modem will always return an 'ERROR' message to the DTE after receiving the +FRM = command.
Range: = 24, 48, 72, 73, 74, 96, 97, 98, 121, 122, 145, 146
(Refer to the Selection Table.)
+FRS none Wait for Silence: The +FRS= 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 is in 10-millisecond intervals. The command will terminate 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 'OK' result code will be returned by the DTE.
Range: = 1 - 255 (10 milliseconds)
+FRTn none Fax Receive Test Command: This command causes the DCE to go off- hook and check for the training sequence for the specified data rate as defined by 'n'. After detecting the appropriate training sequence, the DCE will send an 'OK' message to the DTE followed by the received data. Typically, the DTE will display this data to the CRT or monitor. The displayed data can then be observed for correctness. Any received character from the DTE or loss of remote data carrier will cause the DTE to terminate the test and remain off-hook. To hangup, send 'ATH' to the modem. Before Issuing the +FRTn command, the DTE must initialize the test command by sending an ATH command. The ATH command only needs to be issued once after power-up. The 'FRTn command is used in conjunction with the '+FTTn' command.
n = 24, 48, 72, 73, 74, 96, 97, 98, 121, 122, 145, 146
Back-to-back tests (no dialing)
Modem 1 Modem 2
AT H +FRT96 AT+FTT96
CONNECT [Send modem generated pattern] CONNECT
OK OK
Dial-up tests
Modem 1 Modem 2
ATH ATDT;
RING AT H +FRT96
AT+FTT96 CONNECT [Send modem generated pattern]
CONNECT
OK OK
+FTH none Transmit HDLC Data: The +FTH = command causes the modem to transmit data framed in HDLC protocol using the modulation mode selected. may have the values shown in the Selection Table.
After receiving the +FTH command, the modem will send a 'CONNECT' result code to the DTE, and transmit signal converter training (if required) followed by flags until the first byte of data is sent by the DTE. The modem terminates this command upon detecting characters in the data stream.
When the buffer becomes empty the modem will compute and append the Frame Check Sequence (FCS) and a closing flag to the frame. The modem will insure that the minimum number of flags required by T.30 are sent before the data from the DTE begins to be transmitted.
The modem will check 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 will cease transmitting after the frame is sent, return to command state, and send the 'OK' result code to the DTE. If the Final Frame bit is a '0', the modem will send the 'CONNECT' result code to the DTE after the frame is sent and then continue to transmit flags until one of the following actions is taken by the DTE:
If the DTE sends additional data, the modem will transmit another frame.
If the DTE sends only (a null frame), the modem will turn off the transmit carrier and send the 'OK' result code to the DTE.
If 5 seconds has elapsed from the time when the modem reported the 'CONNECT' result code without any additional data transmitted from the DTE, the modem will turn off transmit carrier, return to command mode, and send the 'ERROR' result code to the DTE.
In HDLC transmit mode, the modem performs HDLC transparency functions, FCS generation, and buffers the transmit data. The modem will use the configured method of flow control to pause the DTE as necessary.
NOTE: If the modem is on-hook, then the modem will always return an 'ERROR' message to the DTE after receiving the +FTH = command.
Range: = 3
(Refer to the Selection Table.)
+FTM none Transmit Data: The +FTM = command causes the modem to transmit data using the modulation selected in the .
The modem returns a 'CONNECT' result code and transmits the proper training sequence in the selected mode, followed by constant '1' bits until data is received from the DTE. The modem terminates this command upon detecting characters in the data stream.
If the modem transmit buffer becomes empty and the last transmitted character is an ASCII NULL (00), the modem will continue to transmit NULLs until the DTE sends more data or 5 seconds has elapsed. After 5 seconds has elapsed with an empty transmit buffer, the DCE will turn off the transmit carrier and return to command state, while returning an 'ERROR' result code to the modem.
NOTE: Hex $00 replication does not provide the required timing needed for generating the TCF frame (1.5 seconds of 0's). When the modem transmit buffer becomes empty and the last transmitted character was not a NULL, the modem will turn off the transmit carrier, return to command state and send the 'OK' result code to the DTE.
NOTE: If the modem is on-hook, then the modem will always return an 'ERROR' message to the DTE after receiving the +FTM = command.
Range: = 24, 48, 72, 73, 74, 96, 97, 98, 121, 122, 145, 146
(Refer to the Selection Table.)
+FTS none Stop Transmission and Pause: The +FTS= command causes the modem to stop all transmissions. The modem then waits for the specified amount of time, and then sends an 'OK' result code to the DTE. The value is in 10-millisecond intervals.
Range: = 0-255 (in 10-millisecond intervals)
+FTTn none Fax Transmit Test Command: This command causes the DCE to go off-hook send a 'CONNECT' message to the DTE and sends a continuous test pattern to the remote modem at the specified data rate 'n'. Any received character from the DTE will cause the DTE to terminate the test and remain off-hook. This command is used in conjunction with the '+FRTn' command. See '+FTRn' for examples.
n = 24, 48, 72, 73, 74, 96, 97, 98, 121, 122, 145, 146
Pattern (in hex): FF, 21-7F, 0D,0A
20-7F, 0D,0A
:
20-7F, 0D, 0A

Voice Mode 'AT' Commands

The CL-MD1414XX implements a voice mode 'AT' command set that allows a DTE to record and play back voice messages. In addition to the Programmer's Guide, a Voice Application Note is available that shows several examples on how to use these 'AT' commands. Below is a list of supported commands, and a detailed description of each command is provided in Table 1-21.

Voice 'AT' Commands

Each command may be used as follows:

#V? read current setting
#V = ? read permissible settings
#V = set parameter

For example, AT#VCL? is used to determine whether the modem is configured for data (or fax) mode or voice mode. AT#VCL=? is used to determine which voice modes are supported by the modem. AT#VCL=n is used for changing between voice mode and data mode.

The modem exchanges streams of data with the DTE while executing the voice playback (AT#VPY) and record (AT#VRD) commands, and in voice command mode (with either OHREL* or VOREL* active _ AT#VLN=n). During these modes, the DCE looks for and reports to the DTE whenever DTMF, CNG, and dial tones are detected. Detection information and data stream terminators are passed between the DTE and DCE by first sending an ASCII <DLE> character (hex $10) followed by a special character (seeTable 1­19 on the following page). Special characters in the data stream are used in the following way:

any data ..... end of data stream ($10 $03)
any data ..... single $10 in data stream
any data ..... X is a special character (Table 1­20), delete both and X from the data stream