Command Process

The command process starts while the modem is in idle or online command states, and the modem detects a start bit from the DTE. The command process ends under any of the three following conditions:

1. When the start bit is not from an AT, at, A/, or a/; or

2. During the 500 microseconds following the result code, transmission is completed

3. When certain other processes are started (e.g., handshaking or hard reset).

While the command process is active, the modem does the following:

1. Determines the AT Speed and parity

2. Accepts commands and corrections

3. Pauses before starting command execution

4. Executes commands (including sending information text to the DTE)

5. Sends result codes

6. Takes a maximum of 500 microseconds to prepare for another command.

The modem does not send result codes to the DTE during the command process except for the result codes generated by execution of the command line. The RING result code is suppressed.

If the calling line ID function is enabled and an incoming call occurs, the calling line Id is saved but not sent to the DTE if the information is received from the line while the modem is in the command process. There is a command to read the calling line ID later if desired.

You can echo characters from the DTE with the E command. If echoed, the modem sends a received character to the DTE. Characters that are ignored are still echoed if you turn on the echo function with command En. All eight bits of an input are echoed, regardless of parity. In some modem implementations, the duration of bits (pulses) of echoed characters may jitter up to 1/16 of the bit duration at the highest DTE speed.

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