CAN Bit Timing

A CAN message comprises a number of bits. Each individual bit is subdivided into three time segments. The SYNC segment is used by the receiver to maintain synchronous timing with the sender. For this purpose, the receiver checks whether the signal edges are received during the SYNC segment. If the signal edges are received in the SYNC segment, there is synchronism between the sender and receiver. However, if the signal edge does not fall within the SYNC segment, the receiver must resynchronize.

The first time segment TSEG_1 is used to compensate for the maximum signal propagation time in a CAN network. This is derived from the two CAN nodes that are furthest separated in the CAN network. If TSEG_1 is undersized, this results in faulty bus access and leads to problems in acknowledgment. The second time segment TSEG_2 serves as a time reserve for resynchronization. This is needed if the receiver's timing is slower than that of the sender. The time required for TSEG_2 is essentially a function of the quality of the clock generator that is used.