XC908AS60ACFU Motorola Semiconductor Products, XC908AS60ACFU Datasheet - Page 166

• Manufacturer Part Number: XC908AS60ACFU
• Description: MC68HC908AZ60A, MC68HC908AS60A Hcmos Microcontroller Unit Technical Data
• Manufacturer: Motorola Semiconductor Products

System Integration Module (SIM)
9.8.1 SIM Break Status Register
Technical Data
166
;
;
;
;
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 BW, do RTI
BRCLR
TST
BNE
DEC
DEC
PULH
RTI
Address:
The SIM break status register contains a flag to indicate that a break
caused an exit from wait mode.
BW — SIM Break Wait
BW 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 zero to the BW bit clears it.
Reset:
Read:
Write:
This status bit is useful in applications requiring a return to wait mode
after exiting from a break interrupt. Clear BW by writing a logic 0 to it.
Reset clears BW.
5
6
BW,SBSR, RETURN
LOBYTE,SP
DOLO
HIBYTE,SP
LOBYTE,SP
1 = Wait mode was exited by break interrupt
0 = Wait mode was not exited by break interrupt
$FE00
Bit 7
R
R
Figure 9-17. SIM Break Status Register (SBSR)
System Integration Module (SIM)
R
6
= Reserved
;
;
; 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 was exited by break.
R
5
R
4
R
3
NOTE: Writing a logic 0 clears BW
MC68HC908AZ60A — Rev 2.0
R
2
See Note
BW
1
0
MOTOROLA
Bit 0
R