Siemens MC55 AT manual Restrictions on Multiplex mode

Notes

•The write command is used to enter the multiplex mode. The setup of the logical channels is initiated by the TE, i.e. the TE acts as initiator. This means that the TE shall ensure that logical channels are established before any further actions on the channels can be started.

•There is a timeout of five seconds, if the multiplexer protocol is enabled and no multiplexer control channel is established. The GSM engine returns to AT command mode.

•The parameter maximum frame size (N1) of AT+CMUX in GSM 07.10 is fixed to 98 bytes and cannot be changed. All other parameters are not available.

4.8.1Restrictions on Multiplex mode

When the serial interface ASC0 is in multiplex mode, data and fax calls can only be set up on logical channel 1. Due to this restriction, AT commands have a different behavior on channels 2+3 compared to channel 1. Several commands are not available, others return different responses. This section summarizes the concerned com- mands. For general rules and restrictions to be considered in Multiplex mode please refer to [5].

Table 4.1: Availability of AT Commands on Virtual Channels

Command	Behavior on channel 1	Behavior on channel 2+3
+++	not usable, but see note 2)	not usable, but see note 2)
AT+CBST	as described	not usable
AT+CRLP	as described	not usable
AT+CG... (GPRS commands)	as described	see note 3)
AT+F... (Fax commands)	as described	not usable
AT&S	as described	not usable
ATA	as described	no Data Calls
ATD	as described	no Data Calls
ATDI	as described	not usable
ATL	as described	not usable
ATM	as described	not usable
ATO	as described	not usable
ATS6 1)	as described	not usable
ATS7 1)	as described	not usable
ATS8 1)	as described	not usable
ATS10 1)	as described	not usable
ATS18 1)	as described	not usable

1)Siemens GSM engines support the registers S0 - S29. You can change S0,S3,S4,S5,S6,S7,S8,S10 and S18 using the related ATSn commands (see starting from ATS0). The other registers are read-only and for internal use only!

2)The applicability of the +++ escape sequence depends on the customer's external application based on the Mulitplexer Protocol. Recommendations for implementing an appropriate modem status command (MSC) are provided in [5], Section "Escape Sequence".

3)PDP contexts can be defined on any channel, but are visible and usable only on the channel on which they are defined (thus it is not possible to define a context on channel 2 and activate it on channel 3). GPRS connections can be estab- lished on two channels at a time.

MC55_ATC_V04.00	Page 96 of 475	3/17/06
Confidential / Released