Rainbow-electronics ATmega64M1 Manuel d'utilisateur télécharger pdf (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

1 2 ... 174 175 176 177 178 179 180 181 182 183 184 ... 342 343

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Rainbow-electronics ATmega64M1 Manuel d'utilisateur Page 179

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