1 restricted use of at commands in multiplex mode – Siemens MC35 User Manual
Page 86
AT Command Set
MC35_ATC_01_V03.02
Page 86 of 228
13.03.2002
turns 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 avail-
able.
5. Multiplex mode can be terminated by AT^SMSO (,AT^SMSO Switch off
mobile station" pg. 184). 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 [5].
Data, fax and GPRS calls can only be set up on logical channel 1. Due to this restriction, AT com-
mands 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+CG... (GPRS commands) as described
usage not recommended
2)
AT+F.... (Fax commands)
as described
not usable
AT&C
as described
not usable
AT&D
as described
not usable
AT&F
as described
data call parameters not changed
S3, S4 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