Chapter 3. Extended Commands

&A ARQ Result Codes Enable

Function

Command enables/disables display of ARQ result codes if X command argument is 1 or greater (see X command section).

Arguments:

0: "/ARQ" connection result codes are disabled .
1: "/ARQ" connection result codes are enabled [Default].
2: Additional modulation indicator (E.G. V34) in result codes for calls at or above 4800 bps.
3: Protocol of call reported: , LAPM, MNP, or NONE. If modem negotiated for data compression, type of compression is added to the result code: V42BIS, MNP5.

&B DTE Data Rate

Arguments

0: Modem DTE interface rate follows the DCE connection rate [Default].
1: Modem DTE interface follows DTE rate, regardless of DCE connection rate.
2: Fixed for ARQ calls/variable for nonARQ calls. Answer mode only. When the modem goes off hook and answers in ARQ mode, it shifts its serial port rate to the one written in NVRAM. In nonARQ mode it acts as if set to &B0 when answering, and switches its serial port rate to match the call's connection rate.

If no argument is given an argument of 0 is assumed.

Aborting Event

None.

&C Carrier Detect.

Function

Command controls the carrier detect signal from the modem to the computer. On the external form factor, carrier detect is also controlled by DIP switch # 6 upon power up and software reset.

Command Syntax

AT&C <argument>

Arguments

0: Carrier Detect override (CD) is always on.
1: Modem send the carrier detect signal when it connects with another modem and drops the signal when it disconnects.[Default]

If no argument is given an argument of 0 assumed.

DTE Interface

CD will go true if &C1 when a connection is made. CD will return to a false state after the connection is dropped.

&D Data Terminal Ready.

Function

Command controls the DTR signal from the DTE to the modem. On the eternal form factor, DTR is also controlled by DIP switch #1 at power up.

Command Syntax

AT&D <argument>

Arguments

0: DTR override, DTR is always on.
1: Online command mode on DTR low. Modem enters command mode on DTR transition to low state. Returns online when DTR returns high.
2: Computer must send DTR for the modem to accept commands, and dropping DTR terminates a call [Default ]
3: Host must send DTR for modem to accept commands, and dropping DTR terminates any active call and causes modem to do a soft reset.

If no argument is given an argument of 0 is assumed.

&F Load Factory Settings

Function

Command resets command options to factory default ROM settings to RAM.

Arguments

0: Load standard factory configuration.
1: Load factory configuration 1 Hardware Flow Control.
2: Load factory configuration 2 Software Flow Control.

If no argument is given an argument of 0 is assumed.

Other

Below are the differences for the three factory patterns. Any value not listed is the same for all three patterns.

&F/&F0: DTE Speed: 9600 baud; Data Size: 7 bits; Parity: Even; Basic commands: X1; Extended Commands: &A1, &B0, &H0, &I0, &R1
&F1: DTE Speed: 19200 baud; Data Size: 8 bits; Parity: None; Basic Commands: X4; Extended Commands: &A3, &B1, &H1, &I0, &R2
&F2: DTE Speed: 19200 baud; Data Size: 8 bits; Parity: None; Basic Commands: X4; Extended Commands: &A3, &B1, &H2, &I2, &R1

&G Guard Tone

Function

Command results in modem sending a guard tone after 2100 Hz answer tone is sent, during connection sequence. This command applies only to overseas calls at 2400 or 1200 bps.

Arguments:

0: No guard tone sent US/Canada [Default].
1: 550 Hz guard tone follows answer tone. To be activated, requires that argument of B command is 0.
2: Enable 1800 Hz guard tone. To be activated, requires that argument of B command is 0.

If no argument is given an argument of 0 is assumed.

&H Transmit Flow Control

Function

Command enables/disables flow control on transmitting channel.

Arguments

0: Transmit data flow control disabled [Default].
1: Enables hardware flow control (CTS)
2: Enables software flow control XON/XOFF, using characters stored in S22 and S23 for XON/XOFF flow control characters, respectively.
3: Enables hardware and software flow control.

If no argument is given an argument of 0 is assumed.

LED

The CTS LED follows the state of the CTS signal (only).

&I Receive Software Flow Control

Function

Command enables software flow control options.

Arguments

0: Disable XON/XOFF flow control of received data. All ASCII characters are transparent to modem except escape sequence [Default].
1: Modem responds to XON/XOFF characters as defined in S registers 22 and 23, respectively. Modem also passes the characters through to the remote DCE.
2: Modem responds to XON/XOFF characters as defined in S registers 22 and 23, respectively, but does not pass the characters to the remote DCE.
3: Enables HewlettPackard host mode. Modem receives an ENQ (decimal 05 ASCII) character every 80 characters from the host via the RS232 line, and returns an ACK (decimal 06 ASCII) character to the host via the RS232 line under two conditions:
The Modem responds immediately if the transmit buffers are empty.; The Modem will not respond with ACK if transmit buffers are 90% full, but responds with ACK when transmit buffers fall below 30% full.
4: Enables HewlettPackard terminal mode. Modem receives an ENQ from the remote DCE and passes it to the DTE. Modem sends no further data to the DTE until it responds with an ACK.
5: Enables special flow control as follows:
If modem is in errorcorrection mode, it responds the same way as if the argument were 2.; If modem is not in errorcorrection mode, it responds as though the argument was 0, except that it responds to XON/XOFF characters from the remote DCE, and does not pass them to the DTE.

If no argument is given an argument of 0 is assumed.

&K Data Compression

Function

Command enables MNP level 5 or V42bis data compression. Requires that an MNP or a LAPM link has been established.

Arguments

0: Data compression disabled
1: Automatic selection/deselecting. Data compression is enabled if the DTE data rate is higher than the link rate (see &B and &N commands), and the remote DCE either supports MNP level 5 option in the MNP link request or V42bis in the LAPM link request [Default].
2: Data compression enabled. The setting is used to keep the modem from disabling data compression, however for this option to work error control must be enabled ( &M4 or &M5 ).
3: Selective data compression disables MNP data compression, but not MNP error correction. It allows a V42bis connection with compression or an MNP connection without compression.

If no argument is given an argument of 0 is assumed.

&M Error Control and Synchronous Operation

Function

Command enables MNP error control option.

Arguments

0: No error control. MNP or V.42 link request is ignored .
1: RESERVED
2: RESERVED
3: RESERVED
4: Automatic selection between V.42, MNP error control and nonerror controlled data link [Default].
5: Error controlled link. If remote DCE doesn't respond to V.42 or MNP link request, modem disconnects call.

If no argument is given an argument of 0 is assumed.

LED

If &M is set to 4 or 5 and an error correction link is established, the ARQ LED will turn on.

Other

If &M is set to 0, error control will be disabled.

&N DCE Link Rate

Function

Command selects variable or fixed DCE data rates

Arguments

0: Variable link rate. Modem adjusts to remote DCE link rate [Default].
1: Fixed link rate at 300 bps. Modem connects to remote DCE if it operates at this rate.
2: Fixed link rate at 1200 bps. Modem connects to remote DCE if it operates at this rate.
3: Fixed link rate at 2400 bps. Modem connects to remote DCE if it operates at this rate.
4: Fixed link rate at 4800 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.32/V.32bis modulation.
5: Fixed link rate at 7200 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.32bis modulation.
6: Fixed link rate at 9600 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.32/V.32bis .
7: Fixed link rate at 12000 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.32bis modulation.
8: Fixed link rate at 14400 bps. Modem connects to remote DCE if it operates at this rate using, V.34, V.FC or V.32bis modulation.
9: Fixed link rate at 16800 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.FC modulation.
10: Fixed link rate at 19200 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.FC modulation.
11: Fixed link rate at 21600 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.FC modulation.
12: Fixed link rate at 24000 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.FC modulation.
13: Fixed link rate at 26400 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.FC modulation.
14: Fixed link rate at 28800 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.FC modulation.
15: Fixed link rate at 31200 bps. Modem connects to remote DCE if it operates at this rate using V.34 modulation.
16: Fixed link rate at 33600 bps. Modem connects to remote DCE if it operates at this rate using V.34 modulation.
17: Fixed link rate at 33333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
18: Fixed link rate at 37333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
19: Fixed link rate at 41333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
20: Fixed link rate at 42666 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
21: Fixed link rate at 44000 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
22: Fixed link rate at 45333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
23: Fixed link rate at 46666 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
24: Fixed link rate at 48000 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
25: Fixed link rate at 49333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
26: Fixed link rate at 50666 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
27: Fixed link rate at 52000 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
28: Fixed link rate at 53333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
29: Fixed link rate at 54666 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
30: Fixed link rate at 56000 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
31: Fixed link rate at 57333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.

If no argument is given an argument of 0 is assumed.

&P Make/Break Ratio

Function

Command enables one of two possible phone line relay duty cycles used during pulse dialing.

Arguments

0: US/Canada make/break ratio of 39%/61% [Default].
1: UK make/break ratio of 33%/67%.

If no argument is given an argument of 0 is assumed

Other

To call or answer overseas modems at 300 bps, set the modem to ITUT V.21 mode. See S27

&R Receive Data Hardware Flow Control

Function

Command enables options for received data hardware flow control.

Arguments

0: Reserved.
1: RTS signal is ignored [Default].
2: Modem sends data to DTE only if RTS is asserted.

If no argument is given an argument of 0 is assumed.

If DTR and RTS are both not asserted during a data connection, and &R is set to 2, modem sends result codes to DTE. This is because in a Basic program, the only way to drop DTR is by closing the COM port, thus forcing RTS low also. In this case, modem is not allowed to send a "NO CARRIER" result code and go on hook, unless it interprets this combination of events as a warrant to send the no carrier result code.

&S DSR Options

Function

Command selects among three DSR options.

Command Syntax

AT&S <argument>

Arguments

0: DSR is always asserted [Default].
1: DSR is asserted when modem starts a data connection and not asserted when carrier is lost.

If no argument is given an argument of 0 is assumed.

DTE Interface

DSR.

LED

None.

Aborting Events

None.

Other

None.

&T Diagnostic Test

Function

Command controls the diagnostic test modes internal to the modem.

Command Syntax

AT&T <argument>

Arguments:

0: Terminates current test.
1: Initiates analog loop back test at any link rate, modulation, compression or error control. S16=4 may be set for a test pattern. Modem must be offline without any other test in progress such as, S16=1. From offline it will enter test and give a "CONNECT..." message and is ready to receive loop back characters. If the test is denied for one of the above reasons an "ERROR" message is issued. If online when issued modem will drop call and issue a "CONNECT..." and then is ready to receive loop back characte r.
2: RESERVED
3: Initiates digital loop back test at any link rate, modulation, compression or error control, which allows the remote end to test out their transmit and receive paths. All data received by local modem is sent back out. Modem has to be in online command mode, after receiving the command it starts the test and issues an "OK" terminated.
4: Grant remote digital loop back: will allow the local modem to respond to a request for remote digital loop back.
5: Deny remote digital loop back to the remote end requesting loop back.
6: Initiates remote digital loop back at link rates of 2400 or 1200 bps with any compression or error control. Modem must be offhook and in online command mode without any other test in progress such as, S16=1 or 8. If this condition is met, and permission is granted by the remote modem, the modem then enters the state test and issues a "CONNECT..." message. When S16 is set to 4 a test pattern will be sent. If the test is denied for one of the above reasons an "ERROR" message is issued and the modem return s to online command mode.
7: Initiates remote digital loop back with selftest at link rates of 2400 or 1200 bps, with any compression or error control. Modem must be offhook and in online command mode without any other test in progress such as, S16=4. Remote access permission must be granted as well. Modem enters test and issue a "OK" message. Modem then sends out a pattern of repeating "U's which can not be seen by the user as modem stays in online command mode. If the test is denied for one of the above reasons an "ERROR" message is issued and returned to online command mode.
8: Initiates analog loop back with self test at any link rate, modulation, compression or error control. Modem must be offline without any other test in progress such as, S16=1. From offline it will enter test and give a "OK" message. The modem then sends out a test pattern of repeating "U's which can not be seen by the user as the modem stays in online command mode. If the test is denied for one of the above reasons an "ERROR" message is issued. If online when issued, modem will drop call and issue a "CON NECT..." and then be ready to send loop back characters.

Termination for Arguments (must be in online command mode):

1: The test can be terminated by entering one of the following a &T0, or ATH0, lowering DTR, doing this modem will go offline and issue a "OK" response; ATZ will end test and then reset modem; the expiration of the test timer that uses S register 18. Also, by any key if S16=4 was set.
3: The test can be terminated by entering a &T0, which will end test and respond with a "OK" response; or by ATH0 or lowering DTR will end test go offline and issue a "OK" response; or by ATZ will end test, issue a "OK" response and then reset modem; or by the expiration of the test timer that uses S register 18.
6: The test can be terminated by entering a &T0, which will end test and respond with a "OK" response; or by either ATH0 or lowering issue a "OK" response and then reset modem; or by the expiration of the test timer that uses S register 18. Also if S16=4 was set any key entered will abort test.
7: The test can be terminated by entering a &T0, which will end test, give a three digit error count, (error count of 255 is given for errors over 255) and respond with a "OK" response; or by either ATH0 or lowering DTR which will end the test, go offline and issue a "OK" response; or by ATZ will end test, issue a "OK" response and then reset modem; or by the expiration of the test timer that uses S register 18.
8: The test can be terminated by entering a &T0, entering an ATH0, or by lowering DTR. After getting one of these commands, the modem will give a three digit error count. 255 is used for errors greater then 255. The modem will then go offline and issue a "OK" response. An ATZ will end test, issue the above error response and then reset the modem. The test timer (S18) expiration will issue a report and an "OK" response like &T0.

&U DCE Link Rate Floor

Function

Command sets minimum DCE connection data rates. This command work in conjunction with &N. The table below defines the interactions.

	&N=0	&N>0
&U=0 or &U>&N	Modem doesn’t limit connect speed.	Modem connects at &N speed only.
&U>0	Modem connects in range from maximum speed down to &U setting	Modem connects in range from &N setting down to &U setting.

Command Syntax

AT&U <argument>

Arguments

0: Variable link rate. Modem adjusts to remote DCE link rate [Default].
1: Minimum link rate at 300 bps. Modem connects to remote DCE if it operates at this rate.
2: Minimum link rate at 1200 bps. Modem connects to remote DCE if it operates at this rate.
3: Minimum link rate at 2400 bps. Modem connects to remote DCE if it operates at this rate.
4: Minimum link rate at 4800 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.32/V.32bis modulation.
5: Minimum link rate at 7200 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.32bis modulation.
6: Minimum link rate at 9600 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.32/V.32bis .
7: Minimum link rate at 12000 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.32bis modulation.
8: Minimum link rate at 14400 bps. Modem connects to remote DCE if it operates at this rate using, V.34, V.FC or V.32bis modulation.
9: Minimum link rate at 16800 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.FC modulation.
10: Minimum link rate at 19200 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.FC modulation.
11: Minimum link rate at 21600 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.FC modulation.
12: Minimum link rate at 24000 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.FC modulation.
13: Minimum link rate at 26400 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.FC modulation.
14: Minimum link rate at 28800 bps. Modem connects to remote DCE if it operates at this rate using, V.34 or V.FC modulation.
15: Minimum link rate at 31200 bps. Modem connects to remote DCE if it operates at this rate using V.34 modulation.
16: Minimum link rate at 33600 bps. Modem connects to remote DCE if it operates at this rate using V.34 modulation.
17: Minimum link rate at 33333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
18: Minimum link rate at 37333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
19: Minimum link rate at 41333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
20: Minimum link rate at 42666 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
21: Minimum link rate at 44000 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
22: Minimum link rate at 45333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
23: Minimum link rate at 46666 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
24: Minimum link rate at 48000 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
25: Minimum link rate at 49333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
26: Minimum link rate at 50666 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
27: Minimum link rate at 52000 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
28: Minimum link rate at 53333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
29: Minimum link rate at 54666 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
30: Minimum link rate at 56000 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.
31: Minimum link rate at 57333 bps. Modem connects to remote DCE if it operates at this rate using x2 modulation.

If no argument is given an argument of 0 is assumed.

DTE Interface

None.

LED

None.

Aborting Events

None.

&W Write to NVRAM

Function

Command writes current modem configuration to NVRAM. The general intent of this command is that all commands and registers which are not in production test commands or S register 1, are stored in NVRAM.

Command Syntax

AT&W <argument>

Arguments

0: Store to NVRAM pattern 0.
1: Store to NVRAM pattern 1.

If No value is entered with the command, then a value of 0 is assumed.

DTE Interface

None.

LED

None.

Aborting Events

None.

Other

The following command settings are stored in NVRAM:

B, F, M, X

On the internal form factor the following command settings are also stored:

E, Q, V, L

The following extended command settings are stored in NVRAM:

&A, &B, &G, &H, &I, &K, &M, &N, &P, &R, &S, &T (stores &T4 or &T5 only), &Y

On the internal form factor the following command settings are also stored:

&C, &D

The following S register settings are stored in NVRAM:

S0, S2 to S13, S15, S19, S21 to S23, S25, S27 to S36, S38 to S42

The following settings are stored in NVRAM:

&Z0 through &Z3 dial strings, Word length and parity, Data rate

&Y Break Handling

Function

Command enables various methods of handling break sequences when a break is received from DTE or remote DC.

Command Syntax

AT&Y <argument>

Arguments

0: Destructive option. When modem receives break signal from DTE, it clears data from transmit buffer, but does not pass break to the remote DCE. Both local and remote Modems resets data compression tables.
1: Expedited destructive option. When modem receives break signal from DTE, it clears data from transmit buffer and sends break to remote DCE Modem, also resets data compression tables [Default].
2: Expedited nondestructive option. When modem receives break signal from the DTE, it does not clear transmit buffer, but sends break to remote DCE out of sequence.
3: Reserved

If no argument is given an argument of 0 is assumed.

DTE Interface

None.

LED

None.

Aborting Events

None.

&Z Write Dial String to NVRAM

Function

Command writes dial string to NVRAM

Command Syntax

First command syntax is "AT&Zn=s". This command is used to write an input dial string into NVRAM. The parameters n and s are defined as follows:

n: Position 0 through 3 [Default = 0 if no argument for n is given].
s: Dial string up to 36 characters, not including <CR>, "AT" or space characters. Nondial string commands are not allowed in the dial string.

Second command syntax is "AT&Zn=L". This command is used to write a previously input dial string to NVRAM. The parameter n is defined as follows:

Position 0 through 3 [Default = 0 if no argument for n is given].

Third command syntax is "AT&Zn?". This command is used to display the current dial string stored in NVRAM. The parameter n is defined as follows:

n: Position 0 through 3 [Default = 0 if no argument for n is given].

Fourth command syntax is "AT&ZL?". This command is used to display the last executed dial string. There are no parameters for this command.