MC68HC908GT16 Datasheet, PDF (317/412 Pages) Motorola, Inc – Microcontrollers

System Integration Module (SIM)
SIM Registers
SBSW — SIM Break Stop/Wait
This status bit is useful in applications requiring a return to wait or stop
mode after exiting from a break interrupt. Clear SBSW by writing a
logic 0 to it. Reset clears SBSW.
1 = Stop mode or wait mode was exited by break interrupt.
0 = Stop mode or wait mode was not exited by break interrupt.
SBSW can be read within the break state SWI routine. The user can
modify the return address on the stack by subtracting one from it. The
following code is an example of this. Writing 0 to the SBSW bit clears it.
;This code works if the H register has been pushed onto the stack in the break
;service routine software. This code should be executed at the end of the break
;service routine software.
HIBYTE EQU
5
LOBYTE EQU
6
;
If not SBSW, do RTI
BRCLR SBSW,SBSR, RETURN
;See if wait mode or stop mode was exited by
;break.
TST
LOBYTE,SP
;If RETURNLO is not zero,
BNE
DOLO
;then just decrement low byte.
DEC
HIBYTE,SP
;Else deal with high byte, too.
DOLO
DEC
LOBYTE,SP
;Point to WAIT/STOP opcode.
RETURN PULH
RTI
;Restore H register.
MC68HC908GT16 • MC68HC908GT8 — Rev. 2
MOTOROLA
System Integration Module (SIM)
Technical Data
317