Datasheet
V850ES/JG3-H, V850ES/JH3-H CHAPTER 20 CAN CONTROLLER
R01UH0042EJ0500 Rev.5.00 Page 906 of 1513
Aug 12, 2011
20.3 Functions
20.3.1 Determining bus priority
(1) When a node starts transmission:
• During bus idle, the node that output data first transmits the data.
(2) When more than one node starts transmission:
• The node that consecutively outputs the dominant level for the longest from the first bit of the arbitration field has
the bus priority (if a dominant level and a recessive level are simultaneously transmitted, the dominant level is
taken as the bus value).
• The transmitting node compares its output arbitration field and the data level on the bus.
Table 20-9. Determining Bus Priority
Level match Continuous transmission
Level mismatch Continuous transmission
(3) Priority of data frame and remote frame
• When a data frame and a remote frame are on the bus, the data frame has priority because its RTR bit, the last
bit in the arbitration field, carries a dominant level.
Remark If the extended-format data frame and the standard-format remote frame conflict on the bus (if ID28 to ID18
of both of them are the same), the standard-format remote frame takes priority.
20.3.2 Bit stuffing
Bit stuffing is used to establish synchronization by appending 1 bit of inverted-level data if the same level continues for
5 bits, in order to prevent a burst error.
Table 20-10. Bit Stuffing
Transmission
During the transmission of a data frame or remote frame, when the same level continues for 5 bits in the data
between the start of frame and the ACK field, 1 inverted-level bit of data is inserted before the following bit.
Reception
During the reception of a data frame or remote frame, when the same level continues for 5 bits in the data
between the start of frame and the ACK field, reception is continued after deleting the next bit.
20.3.3 Multi masters
As the bus priority (a node which acquires transmission rights) is determined by the identifier, any node can be the bus
master.
20.3.4 Multi cast
Although there is one transmitting node, two or more nodes can receive the same data at the same time because the
same identifier can be set to two or more nodes.