Siemens Mux_guide_v06 Integrating multiplexer into the customer application, Characteristics

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Multiplexer User's Guide

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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 [5] for a detailed description.

3.1 Characteristics

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 setting.

•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.

3.1.2 Restrictions

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.

Mux_guide_v06

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Contents Siemens Cellular Engines Version DocID Muxguidev06Muxguidev06 Document Name Multiplexer Users GuideMultiplexer Users Guide June 30Contents Multiplexer protocol version control TablesDocument history Chapter What is newIntroduction References Supported products and related documentsAbbreviation Description Term and abbreviationsProduct concept and architecture Multiplexer protocol an overviewVirtual channels and AT commands Restrictions CharacteristicsIntegrating multiplexer into the customer application Basic requirementsFunctions without channel dependencies Timing conditions RTS/CTS on the physical channels Multiplexer control and signaling linesFlow control Logical flow controlCOM M COM N COM P RTS/CTS RTS/CTS on the logical channelsEscape sequence Power savingBandwidth of logical channels Data link layer Structure of the multiplexer protocolIntroduction of the multiplexer protocol Address field Flag sequenceFrame Type Control fieldBit Length indicatorInformation field Frame checking sequence field FCSState diagrams Relationship between the customer µC and the GSM engine µC AT+CMUX Serial Interface Customer GSM engineCustomer µC Serial interfaceResponder CustomerEngine GSM engineType field Close-down procedureDLC release Multiplexer control channelLength field Test command TestMultiplexer close down CLD Modem status command MSC Break signal optional Bit Not supported Value octet Length=1 Bit Power saving control PSCCommands Bit Description Type BitNo Value octet Length=0 Non-supported command response NSCValue octet Bit Command Type Non-supported commandAT+CMUX Customer GSM engine µCIntroduction Multiplexer protocol version controlMultiplexer protocol versions Modem status command MSCSignals Break Signals Octet Optional Command Bit Signals BitImplementing version control TroubleshootingExample of TestCommand message Coding of TestCommand message
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