mirror of
https://github.com/cc65/cc65.git
synced 2024-10-31 04:04:49 +00:00
94 lines
1.3 KiB
ArmAsm
94 lines
1.3 KiB
ArmAsm
;
|
|
; Ullrich von Bassewitz, 27.09.1998
|
|
;
|
|
; void set_brk (unsigned Addr);
|
|
; void reset_brk (void);
|
|
;
|
|
|
|
.export _set_brk, _reset_brk
|
|
.export _brk_a, _brk_x, _brk_y, _brk_sr, _brk_pc
|
|
.import brk_jmp
|
|
|
|
.include "plus4.inc"
|
|
|
|
|
|
.bss
|
|
_brk_a: .res 1
|
|
_brk_x: .res 1
|
|
_brk_y: .res 1
|
|
_brk_sr: .res 1
|
|
_brk_pc: .res 2
|
|
|
|
oldvec: .res 2 ; Old vector
|
|
|
|
|
|
.data
|
|
uservec: jmp $FFFF ; Patched at runtime
|
|
|
|
|
|
.code
|
|
|
|
; Set the break vector
|
|
.proc _set_brk
|
|
|
|
sta uservec+1
|
|
stx uservec+2 ; Set the user vector
|
|
|
|
lda #<brk_handler ; Set the break vector to our routine
|
|
sta brk_jmp+1
|
|
lda #>brk_handler
|
|
sta brk_jmp+2
|
|
rts
|
|
|
|
.endproc
|
|
|
|
|
|
; Reset the break vector
|
|
.proc _reset_brk
|
|
|
|
lda #$00
|
|
sta brk_jmp+1
|
|
sta brk_jmp+2 ; Reset the vector
|
|
rts
|
|
|
|
.endproc
|
|
|
|
|
|
|
|
; Break handler, called if a break occurs. Note: Y is not on the stack!
|
|
|
|
.proc brk_handler
|
|
|
|
sty _brk_y
|
|
pla
|
|
sta _brk_x
|
|
pla
|
|
sta _brk_a
|
|
pla
|
|
and #$EF ; Clear break bit
|
|
sta _brk_sr
|
|
pla ; PC low
|
|
sec
|
|
sbc #2 ; Point to start of brk
|
|
sta _brk_pc
|
|
pla ; PC high
|
|
sbc #0
|
|
sta _brk_pc+1
|
|
|
|
jsr uservec ; Call the user's routine
|
|
|
|
lda _brk_pc+1
|
|
pha
|
|
lda _brk_pc
|
|
pha
|
|
lda _brk_sr
|
|
pha
|
|
ldx _brk_x
|
|
ldy _brk_y
|
|
lda _brk_a
|
|
rti ; Jump back...
|
|
|
|
.endproc
|
|
|
|
|