CAN Bus State

All CAN hardware maintains two error counters that are increased when transmit or receive errors are detected, and decreased when successful transmissions or receptions are achieved. In an error free operational system, these counters should be zero. The magnitude of these counters control the following state machine:

When a node is in the Operational state it will participate fully with all communications over the network, as the errors increase the CAN hardware will become Passive (detecting errors but not generating error messages), before turning Off and isolating the node from the network once the TxErrorCount exceeds 255 error messages. This feature allows nodes that are either malfunctioning or not configured correctly to be isolated for the network, thereby allowing the remaining nodes to successfully communicate.