Some simple questuions for CAN bus J1939

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Some simple questuions for CAN bus J1939

DogYi
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Hi, I am a newbie for CAN bus J1939

I have some simple questions which confused me few days...

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(1)
We know that in order to broadcast a multi-packet message, a node must first send a BAM which
PDU format is 236, PDU specific is 255(global address) and PGN is 0x00EC00

However, we said that PGN is composed of 24 bits:
6(always 0) + 1(reserved = 0) + 1(data page = 0) + 8(PF) + 8(PS)

Here is the question: why the PGN is 0x00EC00 but not 0x00ECFF ?

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(2)
What is PGN "proprietary A" and "proprietary B" ?

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(3)
Why we said that parameter groups that contain more than 8 data bytes are transmitted by means of a transport protocol? What is "transport protocol" really do? And what is different between TP.CM and TP.DT?

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(4)
Now, I have CAN devices without J1939 protocol, each device contains two channel which can both send and receive CAN message. Recently, we are trying to support our CAN device with J1939 protocol. Therefore, I start learning about J1939. Some literatures said that "An ECU(electronic control unit) may contain one or more CA(controller application)". What is that means? Is one ECU represent one CAN device? And what is the meaning of CA?


Thanks,
BR