Specifications
AT Command Set
TC3X_ATC_01_V04.00 Page 87 of 204 29.05.2002
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.
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 Behaviour on channel 1 Differences on channel 2+3
+++ as described not usable
ATE as described as described
AT+CBST as described not usable
AT+CR as described not usable
AT+CRLP as described not usable
AT+F.... (Fax commands) not usable not usable
AT&C as described not usable
AT&D as described not usable
AT&F as described data call parameters not changed
AT&S as described not usable
AT&V as described data call parameters not displayed
ATA as described no data calls
ATD as described no data calls
ATDI<n> as described not usable
ATO as described not usable
ATS0
1
)
as described not usable
ATS3
1
)
as described as described
ATS4
1
)
as described as described
ATS5
1
)
as described not usable