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11.8 Functions
11.8.1 Determination of bus priority
(1) When one node has started transmitting
• In bus idle mode, the node that outputs data first starts transmission.
(2) When several nodes have started transmitting
• The node that has the longest string of consecutive "dominant (D)" bits starting from the first bit in the
arbitration field has top priority for bus access ("dominant (D)" bits take precedence due to wired OR bus
arbitration).
• The transmitting node compares the arbitration field which it has output and the bus data level.
Matched levels
Mismatched
levels
(3) Priority between data frame and remote frame
• If a bus conflict occurs between a data frame and a remote frame, the data frame takes priority because its
last bit (RTR) is "dominant (D)".
11.8.2 Bit stuffing
Bit stuffing is when one bit of inverted data is added for resynchronization to prevent burst errors when the same
level is maintained for five consecutive bits.
Transmit
When transmitting data frames and remote frames, if the same level is maintained for five bits
between the start of frame and CRC fields, one bit of data whose level is inverted from the
previous level is inserted before the next bit.
Receive
When receiving data frames and remote frames, if the same level is maintained for five bits
between the start of frame and CRC fields, the next bit of data is deleted before receiving is
resumed.
11.8.3 Multi-master
Since bus priority is determined based on the identifier, any node can be used as the bus master.
11.8.4 Multi-cast
Even when there is only one transmitting node, the same identifier can be set for several nodes, so that the same
data can be received by several nodes at the same time.
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CHAPTER 11 FCAN CONTROLLER
Table 11-8. Determination of Bus Priority
Transmission continues
When a mismatch is detected, data output stops at the next bit, and the
operation switches to receiving.
Table 11-9. Bit Stuffing
User's Manual U14492EJ3V0UD
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