Rainbow Electronics ATmega64M1 - Manual (Page 179)

179
8209A–AVR–08/09
ATmega16M1/32M1/64M1
Figure 20-12. Line Error Mode
Note: More than one REC/TEC change may apply during a given message transfer.
20.8.2 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 acknowl-
edge 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.
ERRP = 1
BOFF = 0
Error
Active
Error
Passive
Bus
Off
TEC > 127 or
REC > 127
128 occurrences
of 11 consecutive
recessive bit
Reset
interrupt - BOFFIT
TEC > 255
TEC < 127 and
REC < 127
ERRP = 0
BOFF = 0
ERRP = 0
BOFF = 1