Restricted Use Of At Commands In Multiplex Mode - Siemens TC37 Module At Command Reference

AT Command Set

4.24.1 Restricted use of AT commands in Multiplex mode

In Multiplex mode, the operation of several AT commands varies from the normal mode. This chapter
summarizes the concerned commands. For general rules and restrictions to be considered in Multiplex
mode please refer to [3].
Data calls can only be set up on logical channel 1. Due to this restriction, AT commands have a
different behaviour on channels 2+3 compared to channel 1. Several commands are not available,
others return different responses. These commands are listed in the table below:
Table 6: Availability of AT commands on virtual channels
Command
+++
ATE
AT+CBST
AT+CR
AT+CRLP
AT+F.... (Fax commands)
AT&C
AT&D
AT&F
AT&S
AT&V
ATA
ATD
ATDI<n>
ATO
1
ATS0 )
1
ATS3 )
1
ATS4 )
1
ATS5 )
TC3X_ATC_01_V04.00
returns to the AT command mode.
3. There are various options to switch from data mode to command mode:
a) Escape sequence +++
b) Circuit 108/2 (DTR) changes from ON to OFF, reaction depends on
command at&d (caution if AT&D0: TA ignores status on DTR).
c) The message Modem Status Command (MSC) for control channel is
defined by the multiplexer protocol GSM07.10. MSC conveys V.24
signals. Bit 3 of Control Signal Octet is DTR, reaction depends on
command at&d (caution if AT&D0: TA ignores status on DTR).
4. The parameter maximum frame size (N1) of AT+CMUX in GSM07.07 is
fixed to 97 and cannot be changed. All other parameters are not
available.
5. Multiplex mode can be terminated with AT^SMSO (Chapter 6.18, pg.
159). It has to be reestablished after power-on.
Behaviour on channel 1
as described
as described
as described
as described
as described
not usable
as described
as described
as described
as described
as described
as described
as described
as described
as described
as described
as described
as described
as described
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Differences on channel 2+3
not usable
as described
not usable
not usable
not usable
not usable
not usable
not usable
data call parameters not changed
not usable
data call parameters not displayed
no data calls
no data calls
not usable
not usable
not usable
as described
as described
not usable
29.05.2002