50.7.4.1.1 CAN Bus Synchronization

Two types of synchronization are distinguished: “hard synchronization” at the start of a frame and “resynchronization” inside a frame. After a hard synchronization, the bit time is restarted with the end of the SYNC_SEG segment, regardless of the phase error. Resynchronization causes a reduction or increase in the bit time so that the position of the sample point is shifted with respect to the detected edge.

The effect of resynchronization is the same as that of hard synchronization when the magnitude of the phase error of the edge causing the resynchronization is less than or equal to the programmed value of the resynchronization jump width (tSJW).

When the magnitude of the phase error is larger than the resynchronization jump width and

  • the phase error is positive, then PHASE_SEG1 is lengthened by an amount equal to the resynchronization jump width.
  • the phase error is negative, then PHASE_SEG2 is shortened by an amount equal to the resynchronization jump width.
Figure 50-6. CAN Resynchronization