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Chapter 19
CAN Controller (CAN)
Preliminary User’s Manual U17566EE1V2UM00
(3)
Synchronizing data bit
• The receiving node establishes synchronization by a level change on the
bus because it does not have a sync signal.
• The transmitting node transmits data in synchronization with the bit timing of
the transmitting node.
(a) Hardware synchronization
This synchronization is established when the receiving node detects the start
of frame in the interframe space.
• When a falling edge is detected on the bus, that TQ means the sync
segment and the next segment is the prop segment. In this case,
synchronization is established regardless of SJW.
Figure 19-20
Adjusting synchronization of data bit
(b) Resynchronization
Synchronization is established again if a level change is detected on the bus
during reception (only if a recessive level was sampled previously).
• The phase error of the edge is given by the relative position of the detected
edge and sync segment.
<Sign of phase error>
0:
If the edge is within the sync segment
Positive:
If the edge is before the sample point (phase error)
Negative: If the edge is after the sample point (phase error)
If phase error is positive: Phase segment 1 is longer by specified SJW.
If phase error is negative: Phase segment 2 is shorter by specified SJW.
• The sample point of the data of the receiving node moves relatively due to
the “discrepancy” in the baud rate between the transmitting node and
receiving node.
S
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a
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Interfr
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CAN
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Bit timing
Ph
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Prop
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S
ync
s
egment
Ph
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