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CAN Controller (CAN)
(2)
Table 18-12
(3)
(4)
Output timing of error frame
Output timing of error frame
Type
Bit error, stuff error,
form error, ACK error
CRC error
Processing in case of error
The transmission node re-transmits the data frame or remote frame after the
error frame. (However, it does not re-transmit the frame in the single-shot
mode.)
Error state
(a) Types of error states
The following three types of error states are defined by the CAN specification:
• Error active
• Error passive
• Bus-off
These types of error states are classified by the values of the TEC7 to TEC0
bits (transmission error counter bits) and the REC6 to REC0 bits (reception
error counter bits) as shown in Table 18-13.
The present error state is indicated by the CAN module information register
(CnINFO).
When each error counter value becomes equal to or greater than the error
warning level (96), the TECS0 or RECS0 bit of the CnINFO register is set to 1.
In this case, the bus state must be tested because it is considered that the bus
has a serious fault. An error counter value of 128 or more indicates an error
passive state and the TECS1 or RECS1 bit of the CnINFO register is set to 1.
• If the value of the transmission error counter is greater than or equal to 256
(actually, the transmission error counter does not indicate a value greater
than or equal to 256), the bus-off state is reached and the BOFF bit of the
CnINFO register is set to 1.
• If only one node is active on the bus at startup (i.e., a particular case such
as when the bus is connected only to the local station), ACK is not returned
even if data is transmitted. Consequently, re-transmission of the error frame
and data is repeated. In the error passive state, however, the transmission
error counter is not incremented and the bus-off state is not reached.
User's Manual U18743EE1V2UM00
Output timing
Error frame output is started at the timing of the bit following
the detected error.
Error frame output is started at the timing of the bit following
the ACK delimiter.
Chapter 18
543
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