CHAPTER 19 FCAN CONTROLLER (V850/SC3)
User’s Manual U15109EJ3V0UD
655
Figure 19-26. Coordination of Data Bit Synchronization
Phase
segment 2
Phase
segment 1
Prop
segment
Sync
segment
Start of frame
Bus idle
CAN bus
Bit timing
(b) Resynchronization
Resynchronization is performed when a level change is detected on the bus during a receive operation
(only when the last sampling was the recessive level).
•
The edge’s phase error is produced by the relative positions of the detected edge and sync segment.
<Phase error symbols>
0:
When edge is within sync segment
Positive:
Edge is before sample point (phase error)
Negative:
Edge is after sample point (phase error)
•
When the edge is detected as within the bit timing specified by the SJW, synchronization is performed
in the same way as hardware synchronization.
•
When the edge is detected as extending beyond the bit timing specified by the SJW, synchronization is
performed on the following basis.
When phase error is positive:
Phase segment 1 is lengthened to equal the SJW
When phase error is negative: Phase segment 2 is shortened to equal the SJW
•
A “shifting” of the baud rate for the transmitting and receiving nodes moves the relative position of the
sample point for data on the receiving node.
Figure 19-27. Resynchronization
Phase
segment 2
Phase
segment 1
Prop
segment
Sync
segment
SOF
Next bit
Previous bit
CAN bus
Bit timing
SJW