Siemens Mux_guide_v06 manual State diagrams

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Multiplexer User's Guide

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4.3 State diagrams

The multiplexer protocol is based on two state machines (see Figure 4). One state machine initiates the setup of the logical channels, the other one responds to the requests.

The GSM engine can only respond to requests. A higher level for controlling the state machines is not implemented.

The procedure for setting up the two state machines – the one for the customer µC and the one for the GSM engine – is shown in Figure 5 and Figure 6.

Executing the AT command AT+CMUX=0 starts the switchover from AT command mode to the multiplexer protocol and parameterizes the multiplexer control channel DLCI = 0. Both state machines are entering the DISCONNECTED state and immediately have the option of setting up the multiplexer control channel DLCI = 0 and other logical channels.

The logical channels are then set up (DLC establishment). If the DLC has been established successfully the state machine for that particular channel changes to CONNECTED. If the request is unsuccessful the logical channel cannot be established and the state machine remains in DISCONNECTED on this particular channel.

Information can be transferred over all channels in CONNECTED. Control commands can be transferred in the multiplexer control channel DLCI = 0; the other channels transfer data.

The parameters for all logical channels DLCI = 1...4 in DISCONNECTED can be set for the requested logical channels by parameter negotiation.

Disconnecting individual channels (DLC release) causes the state machine for those channels to revert to DISCONNECTED. Release of the multiplexer control channel DLCI = 0 corresponds to a CLOSE DOWN. The CLOSE DOWN command switches back.

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Contents Siemens Cellular Engines Version DocID Muxguidev06Multiplexer Users Guide Document Name Multiplexer Users GuideJune 30 Muxguidev06Contents 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 Integrating multiplexer into the customer application CharacteristicsBasic requirements RestrictionsFunctions without channel dependencies Timing conditions Flow control Multiplexer control and signaling linesLogical flow control RTS/CTS on the physical channelsCOM M COM N COM P RTS/CTS RTS/CTS on the logical channelsPower saving Bandwidth of logical channelsEscape sequence Structure of the multiplexer protocol Introduction of the multiplexer protocolData link layer Address field Flag sequenceFrame Type Control fieldInformation field Length indicatorFrame checking sequence field FCS BitState diagrams Relationship between the customer µC and the GSM engine µC AT+CMUX Serial Interface Customer GSM engineCustomer µC Serial interfaceEngine CustomerGSM engine ResponderDLC release Close-down procedureMultiplexer control channel Type fieldTest command Test Multiplexer close down CLDLength field Modem status command MSC Break signal optional Bit Not supported Commands Bit Description Power saving control PSCType Bit Value octet Length=1 BitValue octet Bit Command Type Non-supported command response NSCNon-supported command No Value octet Length=0AT+CMUX Customer GSM engine µCIntroduction Multiplexer protocol version controlSignals Break Signals Octet Optional Command Bit Modem status command MSCSignals Bit Multiplexer protocol versionsImplementing version control TroubleshootingExample of TestCommand message Coding of TestCommand message
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