Paradyne 3821PLUS manual Recovering AT Commands, Type T

COMSPHERE 3821Plus Modem

Recovering AT Commands

Certain dialing methods, such as V.25bis and synchronous operation, disable the use of AT commands and place the modem into a state known as Dumb mode. The 3821Plus is capable of normal operation when in Dumb mode. Moreover, the SDCP normally can be used to load the Async Dial factory default and restore the use of AT commands. However, if an SDCP is for some reason unavailable, the following procedure may be used.

The AT Recovery command (AT***) places the modem into a temporary state that restores AT commands. When in this state, the modem's previous settings are retained except for the following configuration options:

•The DTE Dialer Type configuration option (&M and &Q) is set to AT

•The Async/Sync Mode configuration option (&M and &Q) is set to Async

•The DSR Control configuration option (&S) is set to Forced On

•The LSD Control configuration option (&C) is set to Forced On

If these settings are not appropriate, then change them to a setting compatible with your current application.

The procedures for an AT recovery using an asynchronous terminal or personal computer are listed in the following section. Read through these procedures before performing a recovery:

"Procedure

1.Turn the modem Off and then ON. The modem performs a power-up self-test in which all LEDs light. While this is running, repeatedly press the A key of your DTE's keyboard (or keep the key depressed if your keyboard automatically repeats characters that way). Keep doing this until A's (or a's) appear on your DTE screen. (You may use all uppercase or all lowercase characters.)

At least three consecutive A's must be entered within a 2-second time interval.

If these characters are not echoed back to the DTE screen after the power-up self-test is complete, then the modem is still in Dumb mode and maintains its current configuration. Turn the modem Off and then ON again, and repeat Step 1.

2.Once the characters are echoed back to the DTE,

TYPE: T***

(The case of this character must be consistent with the case used in Step 1. Mixed case prefixes such as aT or At are not recognized.)

This must be entered within 10 seconds after receiving the echoed characters.

PRESS: Enter

The screen displays OK.

The modem is now in AT Recovery mode, and remains in this state until a Save or power reset occurs. While in this mode, you can use AT commands to make any necessary changes to configuration options.

Keep in mind that the &C command is changed to Forced On (&C0), the &M and &Q commands are changed to Async mode with AT commands enabled (&M0 and &Q0), and the &S command is changed to Forced On (&S0). If these settings are not appropriate, then reset them to a desired choice before exiting AT Recovery mode.

3.To save changes, use the &W command:

TYPE: AT&Wn

Where: n is one of the following storage areas:

0 for Active (Saved)

1 for Customer 1

2 for Customer 2

PRESS: Enter

The modem exits AT Recovery mode and returns to its previous application environment. Only the Active (Saved) area affects modem operation. To move a Customer area to Active (Saved), use the Z command.

4-26 January 1999 3821-A2-GB20-40