State Diagrams - Siemens TC3 Series User Manual

TC3x Multiplexer User's Guide

8.3 State Diagrams

The multiplexer protocol is based on two state machines (see Figure 16). One state machine initiates
the setup of the logical channels, while the other responds to the requests.
The TC3x 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
TC3x – is shown in Figure 17 and Figure 18.
The AT command "AT+CMUX=0" starts the switchover from AT command mode to the multiplexer
protocol and parameterizes the muliplexer control channel DLCI = 0. Both state machines are then in
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 establishment is successful 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 for that
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
TC3x_UG_01_V03.10 - Released Page 34/50 10.01.2002