Table of Contents
Advertisement
PN 88300150
Introduction
You may find it necessary sometimes to issue AT commands to your modem while you are on-line with a
remote modem, without disconnecting the call. If so, you will want to take advantage of Escape methods
which allow you to change the modem's mode of operation from On-Line mode to Command mode,
where you may issue AT commands, without disconnecting. While you may then return on-line, typically
most users escape so that they may hang up a modem upon completion of a call.
Our modems offer two Escape Methods: in-band, and out-of-band. Both incorporate Time Independent
Escape Sequence (TIES) methodology. An escape sequence is a pattern, or sequence, that the modem
recognizes as its signal to shift from On-Line mode to Command mode. Time Independent means that
the modem recognizes the escape sequence without a prefixed and/or suffixed delay.
In an in-band escape, the modem recognizes the escape sequence as a pattern sent to it as part of the
data stream or band (hence its name).
In an out-of-band escape, the escape sequence is a pattern that cannot and does not occur in the data
stream.
Our in-band escape method is: +++AT<CR>.
Our out-of-band escape method is: <BREAK>AT<CR>.
A BREAK signal cannot be sent as part of a data file; instead it is sent by a direct program command to
the UART used by that computer.
BREAK is defined as either the transmission of binary 0 for a minimum of 10 bits; or as a minimum
interval of 135 milliseconds as established in the ITU-T X.28 standard. There are routines in high level
languages, and keys on most computers that have been established to send BREAK for fixed intervals,
but you may control the BREAK's duration by refering to your UART's specifications.
How to Select an Escape Method
If you want your modem to escape and then wait for you to issue a command before it will return to On-
Line mode, then use +++AT<CR>. You might use this method if you find you need to review a help
screen in the middle of a communications session.
If you wish to combine the escape with a command (or commands) and with an immediate return to On-
Line mode, then use the <BREAK>AT<CR> method. You may also use this method to have the modem
wait before it will return On-Line.
You may select your modem's escape method by using an AT%E command.
The AT commands used to select the modem's Escape Method are:
%E0 = Escape Disabled
%E1 = +++AT method (default)
%E2 = <BREAK>AT method
4/3/01
APPENDIX J
MULTI-TECH SYSTEMS' ESCAPE METHODS
%E3 = Both escape methods enabled
%E4 = Disable OK response to +++
%E5 = Enable OK response to +++
98
Advertisement
Table of Contents
