XC90 L5-2.5L Turbo VIN 59 B5254T2 (2004)
A data frame consists of different parts. This consists of check data, asynchronous, synchronous and administrative data. A data frame on the MOST
network is 64 bytes. The data frame consists of the following:
1. synchronization of the clock on the MOST network, i.e. the frequency at which data is transmitted so that the data is sent at the correct intervals
2. administrative data, indicates the size of the asynchronous and synchronous data
3. synchronous data
4. asynchronous data
5. control data
6. administrative data.
16 data frames are required to form a block. One block is the minimum size of a MOST message.
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:
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DeviceID - The ID number of one of more control modules in the network
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FBlockID - The ID number of a function unit, for example the CD function in the CD module (MP2)
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InstID - The ID number to differentiate between identical function units, for example two CD modules in the MOST network
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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.
Calculating the transfer rate
The number of "ones" and "zeros" transmitted per second determines the transfer rate.
The number of data frames multiplied by the clock frequency of a frame gives the transfer rate.
Example
