38.3.3.3 Synchronization

To compensate for phase shifts between the oscillator frequencies of the nodes on the CAN bus, each CAN controller must be able to synchronize to the relevant edge of the incoming signal. The CAN controller expects an edge in the received signal to occur within the SYNC segment. Only recessive-to-dominant edges are used for synchronization.

There are two mechanisms used for synchronization:
  • Hard Synchronization – Forces the edge that has occurred to lie within the SYNC segment. The bit time counter is restarted with SYNC.
  • Resynchronization – If the edge falls outside the SYNC segment, PHSEG1 or PHSEG2 will be adjusted.

For a more detailed description of the CAN synchronization, refer to ISO11898-1:2015.