Multiplexer can message
CAN messages are used for sending the information from the ECU to another ECU over the CAN BUS, this is happening based on the request from the ECU else ECU will send the message based on the event trigger.
- Signals are the smallest unit of messages, more than one signal combined frame as message/information.
- If more than one signals frame message, then each signal differentiated by the start bit/byte of the signals in the message.
- Signal multiplexing available in CAN messages, which means that based on multiplexer byte values number of signals in the message gets vary.
- That controlling byte called multiplexor values and it is referred to as multiplexed signals.
- Two types of multiplexing modes are available, these are
- Standard and
- Extended multiplexing
- If only one multiplexer byte available in the message, then that is standard multiplexing
- Where S0 is a multiplexer control byte
- CAN message layout for standard or simple multiplexer message is,
Extended signal multiplexing
- More than one multiplexer control bytes to define the number of signals present in the message
- Where S0 and S1 are multiplexer control byte,
Relate to this SAE J1939:
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