Most Protocol

All activations on the MOST network are control messages or MOST messages. The majority of the MOST messages are initiated by the infotainment control module (ICM). The infotainment control module (ICM) informs certain control modules if a function in the control module should be activated. The infotainment control module (ICM) then creates space on the MOST network for the activations in the control module to transmit data, either synchronous or asynchronous. The structure of a message is as follows:

• DeviceID. FBlockID. InstID. FktID. OPType.

This means:

• DeviceID - The ID number of one of more control modules in the network
• FBlockID - The ID number of a function unit, for example the CD function in the CD module (MP2)
• InstID - The ID number to differentiate between identical function units, for example two CD modules in the MOST network
• FctID - The ID number of the function to be activated, for example play or stop
• OPType - Specifies how the function is to be used, because a function can be used in different ways.

The message may appear as follows:

• MP2. CD.01. Track, Length. Set(10).

This means: play song number 10 on the CD player in the CD module (MP2).

The infotainment control module (ICM) knows which control modules are in the MOST network. It can then assign specific ID numbers to all control modules and the included functions. If control modules are removed or added, the ID numbers for the control modules are re-assigned.