MC68HC08AS32 Datasheet, PDF (344/394 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

Byte Data Link Controller-Digital (BDLC-D)
Since a logic 0 dominates a logic 1, the message with the lowest value
will have the highest priority and will always win arbitration. For instance,
a message with priority 000 will win arbitration over a message with
priority 011.
This method of arbitration will work no matter how many bits of priority
encoding are contained in the message.
During arbitration, or even throughout the transmitting message, when
an opposite bit is detected, transmission is stopped immediately unless
it occurs on the 8th bit of a byte. In this case, the BDLC automatically will
append up to two extra logic 1 bits and then stop transmitting. These two
extra bits will be arbitrated normally and thus will not interfere with
another message. The second logic 1 bit will not be sent if the first loses
arbitration. If the BDLC has lost arbitration to another valid message,
then the two extra logic 1s will not corrupt the current message.
However, if the BDLC has lost arbitration due to noise on the bus, then
the two extra logic 1s will ensure that the current message will be
detected and ignored as a noise-corrupted message.
Advance Information
344
Byte Data Link Controller-Digital (BDLC-D)
MC68HC08AS32 — Rev. 3.0
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