Multiplexer User's Guide
Confidential / Released
3 Integrating multiplexer into the customer application
When designing a multiplexer application, you can create your own sources or take
advantage of the sources delivered upon request by Siemens. The Siemens sources are
packed in a *.zip file which includes a driver for Windows 2000 and Windows XP. See  for
a detailed description.
After establishing the multiplexer mode according to the multiplexer protocol, three logical
channels are available. Please keep the following restrictions and requirements in mind:
3.1.1 Basic requirements
The GSM engine supports the basic option and UIH Framing according to GSM 07.10.
Character framing must be configured for 8 data bits, no parity and 1 stop bit.
If you wish to use multiplexer mode with TC35i modules, be sure not to change this
Hardware flow control AT\Q3 is recommended for use with multiplexer mode. If used, it
needs to be set before multiplexer mode is entered.
Several customer software applications may be able to change the selected settings.
These settings will be stored in the non-volatile memory and used whenever the module
is powered up again. In this case the multiplexer fails to start. To avoid this, it is recom-
mended to re-synchronize all settings before using the multiplexer mode again.
Before closing the multiplexer make sure that there is no ongoing activity on one of the
channels. For example, check that voice, CSD or GPRS connections have ended and
wait until all pending AT command responses are received.
If the GSM engine is operated in multiplexer mode, the following restrictions apply:
MO and MT circuit-switched data and fax calls can only be set up on channel 1.
It is not recommended to use AT+CFUN=<n> for selecting one of the SLEEP modes. For
products supporting Multiplexer Protocol version 3, the best approach to properly control
SLEEP mode in this case is to issue the PSC messages described in Chapter 4.3.10.
The multiplexer cannot be started if one of the following features is activated, nor can these
features be used when multiplexer is active:
Multiplex mode cannot be started while autobauding (AT+IPR=0) is enabled.
The multiplexer is not available in charge-only mode and in alarm mode.
XON/OFF flow control is not supported in multiplexer mode.
The maximum frame size N1 (defined in GSM 07.10) is fixed to 98 bytes and cannot be
changed. The maximum frame size is the same for sending and receiving. See also Chapter
4 in this manual and GSM 07.10.
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