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XE2401L

2400bps Serial Input Component Modem

Xecom 

AT Commands

The XE2401L uses "AT" commands for

configuration and control. This section describes

use of the AT command format and lists the AT

commands, Registers and Result codes.

Modes of Operation

The "AT" commands have two operational

modes; Command Mode and Data Mode.

Data Mode: The XE2401L enters data mode

after it connects with a remote modem and issues

an appropriate "CONNECT" result code. In the

Data Mode the modem sends all data presented

on Transmit Data (TXD) to the remote modem

and puts data from the remote modem onto

Received Data (RXD). When the modem exits

data mode, it issues a "NO CARRIER" result

code.

Command Mode: The XE2401L enters

command mode on power-up, reset, a lost

connection, or receipt of the escape code. In

command mode the modem accepts commands

from the host on transmit data. Appropriate result

codes are returned on received data.

Command Line Format

Command lines issued to the modem follow a

strict format. Each command begins with the

prefix AT. The command line is stored in the

command buffer and executed upon receipt of a

carriage return. Until executed, the command

line can be editied with the backspace key.

Speed is determined by measuring the width of

the incoming bits. Parity is determined by

comparing the parity bit of the "A" and the "T."

Command Line - Commands may be strung

together in a single command line of up to 40

characters. Commands are executed in the

sequence they appear. Spaces may be inserted

into the command line but do not fill space in the

command buffer. A carriage return terminates the

command line and causes the commands to be

executed. Register S3 allows the user to select a

character other than a carriage return to terminate

the command line.

Command Buffer - No more than 40 characters,

including the AT prefix, may be loaded into the

command buffer. If the command buffer

overflows, the modem issues an "ERROR" result

code and commands are not executed.

Command Line Editing - The backspace can be

used to edit a command line before it is executed.

The backspace key, (Control and H

simultaneously on some systems), erases the

previous character in the command line. Register

S5 allows the user to select a character other

than a backspace to edit the command line.

Re-Execute Last Command - The A/ command

causes the modem to reexecute the last

command line. This is the only command which

does not require the "AT" prefix.

Command Prefix - Each command, except the

A/ command, begins with the AT prefix. The "A"

and "T" may be either both upper case or both

lower case but cannot be of different cases. The

prefix identifies the speed and parity of the

commands sent to the modem by the host.

Ommitted Parameters - Most commands include

a parameter which determines how the functions

will be set. When the command parameter is

omitted from the command string, it is assumed to

be a 0.

4/XECOM

XE2401L

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