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XE2420G

Smallest World-Wide 2400 BPS Modem

Unspecified 

XE2420G AT Commands

The XE2420G uses "AT" commands for modem control

and configuration. This section describes the AT

command format and lists the AT commands, Registers

and Result codes.

Data Mode: The XE2420G enters data mode after

establishing a remote modem connection and issuing

the appropriate 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 XE2420G 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 buffer stores the command line and executes it

upon receipt of a carriage return. Until executed, the

command line can be edited with the backspace key.

Command Prefix - Each command, except the A/

command, begins with the AT prefix. The "A" and "T"

may be 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. The modem

determines data rate by measuring the width of the

incoming bits. Parity is determined by comparing the

parity bits of the "A" and the "T."

Command Line - Commands may be strung together in a

single command line of up to 48 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 - The Command Buffer holds a

maximum of 48 characters, including the AT prefix. If the

command buffer overflows, the modem issues an

"ERROR" result code and commands are not executed.

Command Line Editing - The backspace edits 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 re-execute the last command line. This is

the only command which does not require the "AT"

prefix.

Omitted 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.

Escape Characters - A 3 character escape sequence may

be entered to switch the modem into command mode

while on line. The escape character, set by Register S2,

must be entered 3 times in succession to execute the

escape. An AT command must then be entered within the

period defined by S12 to enter command mode. The

default escape sequence is "+++."

Result Codes - The modem issues a result code after

each action. Result codes may be sent as full words, one

or two digit numeric codes, or may be disabled all

together. Each result code ends with a carriage return

when numeric result codes are chosen. When full word

result codes are chosen, a Line Feed and Carriage Return

precede and follow each result code.

XECOM

(10)

XE2420G

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