mc68hc908sr12 Freescale Semiconductor, Inc, mc68hc908sr12 Datasheet - Page 162

• Manufacturer Part Number: mc68hc908sr12
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

System Integration Module (SIM)
9.8.1 SIM Break Status Register
Data Sheet
162
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
LOBYTE
DOLO
RETURN
EQU
EQU
If not SBSW, do RTI
BRCLR
TST
BNE
DEC
DEC
PULH
RTI
SBSW,SBSR, RETURN
LOBYTE,SP
DOLO
HIBYTE,SP
LOBYTE,SP
Note: Writing a logic 0 clears SBSW.
Address:
The SIM break status register (SBSR) contains a flag to indicate that a
break caused an exit from stop mode or wait mode.
SBSW — Break Wait Bit
SBSW can be read within the break interrupt routine. The user can
modify the return address on the stack by subtracting 1 from it. The
following code is an example.
Reset:
Read:
Write:
This status bit is set when a break interrupt causes an exit from wait
mode or stop mode. 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
$FE00
Bit 7
R
Figure 9-20. SIM Break Status Register (SBSR)
System Integration Module (SIM)
R
6
;
;
;If RETURNLO is not zero,
;then just decrement low byte.
;Else deal with high byte, too.
;Point to WAIT/STOP opcode.
;Restore H register.
See if wait mode or stop mode was exited by
break.
R
R
5
MC68HC908SR12•MC68HC08SR12 — Rev. 5.0
= Reserved
R
4
R
3
Freescale Semiconductor
R
2
SBSW
Note
1
0
Bit 0
R