MC68HC08AS32 Datasheet, PDF (350/394 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

Byte Data Link Controller-Digital (BDLC-D)
Bus Fault
If a bus fault occurs, the response of the BDLC will depend upon the
type of bus fault.
If the bus is shorted to battery, the BDLC will wait for the bus to fall to
a passive state before it will attempt to transmit a message. As long
as the short remains, the BDLC will never attempt to transmit a
message onto the J1850 bus.
If the bus is shorted to ground, the BDLC will see an idle bus, begin
to transmit the message, and then detect a transmission error ($1C in
BSVR), since the short to ground would not allow the bus to be driven
to the active (dominant) SOF state. The BDLC will abort that
transmission and wait for the next CPU command to transmit.
In any case, if the bus fault is temporary, as soon as the fault is
cleared, the BDLC will resume normal operation. If the bus fault is
permanent, it may result in permanent loss of communication on the
J1850 bus. (See 20.7.4 BDLC State Vector Register.)
BREAK — Break
If a BREAK symbol is received while the BDLC is transmitting or
receiving, an invalid symbol ($1C in BSVR) interrupt will be
generated. Reading the BSVR register (see 20.7.4 BDLC State
Vector Register) will clear this interrupt condition. The BDLC will wait
for the bus to idle, then wait for a start-of-frame (SOF) symbol.
The BDLC cannot transmit a BREAK symbol. It can only receive a
BREAK symbol from the J1850 bus.
Advance Information
350
Byte Data Link Controller-Digital (BDLC-D)
MC68HC08AS32 — Rev. 3.0
MOTOROLA