Operating Modes; Command Mode - At Commands - Thermo Scientific V.22/212A User Manual

Modem card for remote telemetry system

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3.2 OPERATING MODES

The modem functions in one of two modes: Command Mode or On-Line Mode. Upon initialization,

the modem enters the command mode of operation. During the command mode the modem

operations are controlled by the AT commands. No data is being received or transmitted while in

the command mode. The modem goes into the on-line mode after making connection with a remote

system and data is transmitted and received.

During the on-line mode of operation the mode can be temporarily interrupted to adjust operating

parameters while maintaining connection with the remote system. An Escape Sequence of three

pluses (+++) from the keyboard or software interrupts the exchange of data, places the modem in the

command mode, and maintains on-line connection with the remote system. After parameters are

changed using the AT commands of the command mode, the modem returns to full on-line

operations when the "ATO0" command is entered.

The command mode uses AT commands to configure and operate the modem. Each command

requires the letters AT as a prefix. For example, to view the current value of S-Register #0 enter the

command "ATS0?". The only exception is the Repeat Command (A/). When "A/" is typed in, the

modem repeats the last command line entered; the AT prefix and the <CR> is not required.

The command can be entered in all capital (ATS0?) or all lower case letters (ats0?), but not mixed

(Ats0?). The AT commands are executed when the Carriage Return Key (<CR>) is pressed. Refer

to the Reference Material Section for a table of AT commands.

Many of the AT commands require a specified parameter to be entered with the command. For

example, the Echo Command requires the number 0 or 1 to be entered with the command to set the

command to be off or on (ATE0 for echo off or ATE1 for echo on). If no parameter is included

when the command is entered, the modem uses a default parameter of 0.

Some commands require a numeric value to be entered with the command. Such as the command to

set the modem to answer on a specific number of rings. The S-Register #0 sets the count for the

number of rings to answer on. To change the count of the S-Register #0 to three rings, enter the

command ATS0=3 (three being the specified numeric value).

The command line can contain as many as 40 characters (spaces, the AT prefix, and the carriage

return are not counted) and activate one or more AT commands. For example, a user wants to set

the echo on and the configure the modem to answer on the third ring. The commands can be entered

as two separate commands both requiring the AT prefix as follows:

ATE1 <CR>

ATS0=3 <CR>

Or the commands can be entered on the same command line sharing the AT prefix as follows:

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