CAN/CANopen® FAQ

Q: Why do most CANopen® applications use CAN 2.0A (11-bit identifiers) and not CAN 2.0B (29-bit identifiers)?

A: CANopen® was specified to support both protocol variants, however - switching to the 29-bit identifiers has several consequences:

1. As only the address field is extended, but not the data field, the overall available data bandwidth decreases. More bits of overhead were added to each message.
2. The overall reliability decreases, as the CRC checksum in each message now needs to cover 18 bits more.
3. The worst case delay for high priority messages becomes longer. Even a low priority message can not be interrupted or aborted once it won arbitration to the bus. And the maximum length of messages on the bus was now increased by 18 bits.

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