> 4.3 | State Diagrams

> The multiplexer protocol is based on two state machines (see Figure 5). One state machine initiates the setup of the logical channels, the other one responds to the requests.
> The module 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 wirelesse module – is shown in Figure 6 and Figure 7.
> 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 terminates the Multiplex mode, and the module reverts to AT command mode.
> Figure 5: Relationship between the customer µC and the module µC
> Figure 6: MPI-Startup, DLC establishment and information transfer
> Figure 7: MP - DLC release and close down