User manual

AT COMMAND SET

Section 4

4-4

1. Idle State

This state is entered shortly after power is applied to the modem and the power-up

self test has been passed. It can also be entered after the modem has executed a non-

dialling command line. In this state, the modem is waiting to autobaud an AT

sequence from the DTE or awaiting a ringing signal from the telephone line. If a

valid 'AT' entry is detected, the modem enters the Command State.

If a valid ringing signal is detected the modem will send a RING message to the

DTE at the last autobaud speed. If set to answer (S-Register 0 not set to 0) the

modem will go off-hook and enter the Data State after a predetermined number of

rings (S0).

2. Command State

During the Command State, the modem buffers command characters from the DTE

until a carriage return (

) character is received. The modem will buffer up to

48 characters not including the initial 'AT' characters. If more than 48 characters are

received the modem will insert a carriage return character and return an ERROR

message signifying buffer overflow. If no overflow is detected and a carriage return

character is received the modem will start to sequentially execute commands in the

buffer until one of the following:

1. Carriage Return Detected

If this is part of a dial command, the DPX-213 will execute the following

sequence: go off-hook, look for dial tone (unless set to blind dial) and then

proceed to place the call.

2. Illegal Command Encountered

The modem will execute the following sequence: send an ERROR message to

DTE, empty the command buffer and return to idle state.

3. Answer (ATA) or On-line (ATO) Command Received

The modem will enter the Data State.