Question:
What will happen if the same input identifiers are assigned to several CAN channels (e. g. CAN-IN2 and CAN-IN3) within one CAN participant?
Answer:
The transferred information is only available to one of the CAN channels within a controller.
The send and receive identifiers of the CAN channels within one CAN participant are stored in the CAN controller of the CAN participant. A standard CAN controller has 16 CAN registers. Consequently, the CAN controller can send and receive on 8 different channels.
Procedure when the CAN telegrams arrive:
The identifier of incoming CAN telegrams are step by step compared to the identifiers stored in the input registers. The first match leads to an assignment of the transferred information to the corresponding CAN channel. The other input registers will not be examined anymore, and the transfer of the CAN telegram is finished.
Consequence:
If the same receive identifiers are assigned to
several CAN channels within one CAN participant, the transferred information will be available
only to the first CAN channel with the matched identifier.
Example for the realized distribution of the CAN channels within one CAN participant on the basis of an 8200 vector with field bus function module of type E82ZAFCC:
- 1 NMT channel (network management telegram)
- 1 Sync channel (SYNC-IN and SYNC-OUT)
- 3 PDO channel (CAN-IN1 to CAN-IN3, CAN-OUT1 to CAN-OUT3)
- 2 SDO channel (SDO-IN1 and SDO-IN2, SDO-OUT1 and SDO-OUT2)
This structure uses 7 of 8 available CAN channels.
