XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 257

• Manufacturer Part Number: XC912BC32CFU8
• Description: M68HC12B Family Data Sheet
• Manufacturer: Motorola Semiconductor Products

M68HC12B Family — Rev. 8.0
MOTOROLA
NOTE:
NOP instructions are used only to align the JMP instructions onto 4-byte
boundaries so that the value in the BSVR can be used intact. Each of the service
routines must end with an RTI instruction to guarantee correct continued operation
of the device. The first entry can be omitted since it does not correspond to an
interrupt.
followed by a write to the BDLC BDR register, or by setting the TEOD bit in
BCR2. Clearing an invalid symbol flag requires an EOF flag to be received
before the BDLC can receive or transmit. If ALOOP or DLOOP in BCR2 is set,
the BDLC node is disengaged from the J1850 bus. Therefore, the BDLC does
not receive any data from the J1850 bus which normally generates BSVR flags.
Upon receiving a BDLC interrupt, the user may read the value within the BSVR,
transferring it to the CPU’s index register. The value can be used to index a jump
table to access a service routine. For example:
The service routines should clear all of the sources that are causing the pending
interrupts. Clearing a high priority interrupt may still leave a lower priority
interrupt pending, in which case bits I0, I1, and I2 of the BSVR reflect the source
of the remaining interrupt request.
If fewer states are used or if a different software approach is taken, the jump
table can be made smaller or omitted altogether.
SERVICE LDX
*
*
JMPTAB JMP
Byte Data Link Communications (BDLC)
JMP
NOP
JMP
NOP
JMP
NOP
.
.
.
JMP
END
BSVR
JMPTAB,XEnter service routine,
SERVE0Service condition #0
SERVE1Service condition #1
SERVE2Service condition #2
SERVE8Service condition #8
Fetch State Vector Number
(must end in an RTI)
Byte Data Link Communications (BDLC)
BDLC Registers
Data Sheet
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