Specifications

Cascade Modem Manual

Page 13

3. Modem Control

3.1. AT Command Format

The Cascade Modem may be controlled by sending serial ASCII command sequences. After execution of the

command, the modem returns a status message to indicate command is executed.

Training the Modem

The modem must be trained to match the DTE speed and parity so that it is able to recognize serial asynchronous

commands sent to it. The modem is trained by sending it the following three character sequence.

AT[CR]

Where: A and T is upper case, [CR] represents carriage return. The modem will respond with one of the following

status messages, depending on whether it is optioned for abbreviated or English status messages:

0[CR] (Abbreviated form)

[CR][LF][OK][CR][LF] (English form)

Where: [CR] represents carriage return (ASCII 13), [LF] represents line feed (ASCII 10). The modem may be

retrained any time while it is idle.

Another attention sequence “A/” is much like the “AT” sequence except it repeats the previously entered command

specified with an “AT” prefix. When given, it must also be in upper case ASCII. No carriage return is needed.

The modem will come up in its default state - 19200 baud on power up, or when reset is initiated by the command

(ATZ). If desired, any speed, error correction, or data compression can be locked in, using the AT\Nn and/or

AT+Ms command.

THE COMMAND FORMAT

Typical commands consist of three elements, the attention sequence, the commands themselves, and a terminating

carriage return.

AT[commands][CR]

When entering commands to the modem, the backspace character - control-H (ASCII 8) - can be used to edit

mistakes. “AT” and “A/” may not be edited however.

Multiple commands may be placed in the command line. A command line may be as long as 37 characters,

excluding AT. The command below instructs the modem to configure itself to not echo characters in the command

mode (E0) and then go to answer mode. Note the lack of punctuation between string commands, and spaces are

ignored.

ATE0A[CR]

The modem supports the AT Command set with extensions and can operate with industry standard

communication software. The commands are compatible with TR302.2/88-08006.