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cc65/libsrc/c128/break.s
cuz e02b3e91c8 Use a destructor instead of atexit
git-svn-id: svn://svn.cc65.org/cc65/trunk@515 b7a2c559-68d2-44c3-8de9-860c34a00d81
2000-12-01 17:58:40 +00:00

126 lines
1.9 KiB
ArmAsm

;
; Ullrich von Bassewitz, 27.09.1998
;
; void set_brk (unsigned Addr);
; void reset_brk (void);
;
.export _set_brk, _reset_brk
.destructor _reset_brk
.export _brk_a, _brk_x, _brk_y, _brk_sr, _brk_pc
.importzp ptr1
.include "c128.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
; Where will we put the break stub?
stub_addr = $0E00 ; BASIC sprite area
; Set the break vector
.proc _set_brk
sta uservec+1
stx uservec+2 ; Set the user vector
lda oldvec
ora oldvec+1 ; Did we save the vector already?
bne L2 ; Jump if we installed the handler already
lda BRKVec
sta oldvec
lda BRKVec+1
sta oldvec+1 ; Save the old vector
ldy #stub_size-1 ; Copy our stub into the low mem area
L1: lda brk_stub,y
sta stub_addr,y
dey
bpl L1
L2: lda #<stub_addr ; Set the break vector to our stub
sta BRKVec
lda #>stub_addr
sta BRKVec+1
rts
.endproc
; Reset the break vector
.proc _reset_brk
lda oldvec
bne @L1
ldx oldvec
beq @L9 ; Jump if vector not installed
@L1: sta BRKVec
stx BRKVec+1
@L9: rts
.endproc
; Break handler, called if a break occurs
.proc brk_handler
pla
sta _brk_y
pla
sta _brk_x
pla
sta _brk_a
pla
and #$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
brk_stub:
.org stub_addr
pla ; Get original MMU value
sta MMU_CR ; Re-enable our config
jmp brk_handler ; Jump to the user handler
.reloc
stub_size = * - brk_stub