BAT32G1x9 user manual | Chapter 22 CAN control
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Rev.1.02
22.3 function
22.3.1
Bus prioritization
(1) When a node starts transmitting:
- When the bus is idle, the
sending node sends the data first
(2) When multiple nodes start transmitting:
- The node that continuously outputs the longest dominant bit starting from the first bit of the arbitral field gets
the bus priority (if the dominant and recessive bits are transmitted at the same time, the dominant bit is used
as the bus value).
- The transport node compares its output Arbitration field to the data level on the bus
Table22-9. Bus Priority Configuration
Level matching
Continuous transmission
Levels do not match
When a mismatch is detected, the transmission is stopped, and then the next bit begins to receive
(3) The priority of data frames and remote frames
- When a data frame and a remote frame are on the bus at the same time, the data frame has precedence
because the RTR bit of the data frame (the last bit of the arbitral field) is the dominant bit.
Note If the extended format data frame and the standard format remote frame conflict on the bus (if ID18
through ID28 are the same), the standard format remote frame has priority.
22.3.2
Bit padding
Bit padding is when the level of the same polarity lasts 5 bits, and then a bit with opposite polarity is
inserted to establish synchronization to prevent bursting errors.
Table22-10. Bit stuffing
Send
When sending a data frame or a remote frame, if 5 identical bits appear consecutively in the data between
the start of the frame and the ACK field, a bit with opposite polarity is inserted before the next bit.
reception
When receiving a data frame or a remote frame, when the data between the start frame and the ACK field
appears consecutively the same 5 bits, the next bit is deleted to continue receiving data.
22.3.3
Multi-master
Because the bus priority (the node that gets the transport capability) is determined by the identifier, either
node can act as the master of the bus.
22.3.4
Multicast
Even if there is only one transport node, two or more nodes can receive the same data at the same time
because the same identifier can be set on two or more nodes.
22.3.5
CAN sleep mode /CAN stop mode function
THE CAN sleep/CAN stop mode puts the CAN controller into wait mode for lower power consumption.
CAN sleep mode can wake up from bus operation, but CAN stop mode cannot be woken up by bus
operation (CAN stop mode is controlled by the CPU).