16.7.2 Error Types
●
BERR: Bit error. The bit value which is monitored is different from the bit value sent.
Note:
Exceptions:
- Recessive bit sent monitored as dominant bit during the arbitration field and the acknowledge slot.
- Detecting a dominant bit during the sending of an error frame.
●
●
SERR: Stuff error. Detection of more than five consecutive bit with the same polarity.
CERR: CRC error (Rx only). The receiver performs a CRC check on every destuffed received message from the start
of frame up to the data field. If this checking does not match with the destuffed CRC field, an CRC error is set.
●
FERR: Form error. The form error results from one (or more) violations of the fixed form of the following bit fields:
●
●
●
●
●
CRC delimiter
acknowledgement delimiter
end-of-frame
error delimiter
overload delimiter
●
AERR: Acknowledgment error (Tx only). No detection of the dominant bit in the acknowledge slot.
Figure 16-13. Error Detection Procedures in a Data Frame
Arbitration
Bit error
Stuff error
Form error
Tx
ACK error
CRC
del.
ACK
del.
SOF
RTR
ACK
EOF
inter.
Identifier
Control
Message Data
CRC
Bit error
Stuff error
Form error
CRC error
Tx
16.7.3 Error Setting
The CAN channel can detect some errors on the CAN network.
●
In transmission:
The error is set at MOb level.
●
In reception:
●
The identified has matched:
The error is set at MOb level.
The identified has not or not yet matched:
The error is set at general level.
●
●
●
After detecting an error, the CAN channel sends an error frame on network. If the CAN channel detects an error frame on
network, it sends its own error frame.
154
ATmega16/32/64/M1/C1 [DATASHEET]
7647O–AVR–01/15
MICROCHIP [ MICROCHIP ]
