Motorola MC68302 User Manual page 197

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3. CRC1 (Header CRC) Error. When this error occurs, the channel writes
the received CRC to the data buffer, closes the buffer, sets the CRC error
(CR) bit in the BD, generates the RBK interrupt (if enabled), and incre-
ments the error counter (CRC1 EC).
When this error occurs on data- and maintenance-message header fields,
the channel will enter hunt mode immediately. It is possible that a
SYN1-SYN2-(SOH,DLE,ENQ) sequence in data will be incorrectly inter-
preted as the start of the next header, but this "header" will have a CRC
error.
4. CRC2 (Data or Maintenance CRC) or CRC3 (Control Message) Error.
When this error occurs, the channel writes the received CRC to the data
buffer, closes the buffer, sets the CRC error (CR) bit in the BD, and
generates the RBK interrupt (if enabled). The channel also increments
the CRC2EC counter.
5. Framing Error. A framing error is detected by the DDCMP controller
when no stop bit is detected in a received data string. When this error
occurs, the channel writes the received character to the buffer, closes
the buffer, sets the framing error (FR) bit in the BD, and generates the
RBK interrupt (if enabled). When this error occurs, parity is not checked
for this character.
The channel will enter hunt mode immediately. It is possible that a
SYN1-SYN2-(SOH,DLE,ENQ) sequence in data will be incorrectly inter-
preted as the start of the next header, but this "header" will have a CRC
error.
NOTE
This error can occur only on asynchronous links.
6. Parity Error. When a parity error occurs, the channel writes the received
character to the buffer, closes the buffer, sets the parity error (PR) bit
in the BD, and generates the RBK interrupt (if enabled).
The channel will enter hunt mode immediately. It is possible that a SYN 1-
SYN2-(SOH,DLE,ENQ) sequence in data will be incorrectly interpreted
as the start of the next header, but this "header" will have a CRC error.
NOTE
This error can occur only on asynchronous links.
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