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|
;
; 2012-01-18, Oliver Schmidt
; 2015-08-22, Greg King
;
; void __fastcall__ set_irq (irq_handler f, void *stack_addr, size_t stack_size);
; void reset_irq (void);
;
.export _set_irq, _reset_irq
.interruptor clevel_irq, 1 ; Export as low priority IRQ handler
.import popax, __ZP_START__, jmpvec
.include "zeropage.inc"
.macpack generic
; ---------------------------------------------------------------------------
.data
irqvec: jmp $00FF ; Patched at runtime
; ---------------------------------------------------------------------------
.bss
irqsp: .res 2
zpsave: .res zpsavespace
; ---------------------------------------------------------------------------
.code
.proc _set_irq
; Keep clevel_irq from being called right now
sei
; Set irq stack pointer to stack_addr + stack_size
sta irqsp
stx irqsp+1
jsr popax
add irqsp
sta irqsp
txa
adc irqsp+1
sta irqsp+1
; Set irq vector to irq_handler
jsr popax
sta irqvec+1
stx irqvec+2 ; Set the user vector
; Restore interrupt requests and return
cli
rts
.endproc
.proc _reset_irq
lda #$00
sta irqvec+2 ; High byte is enough
rts
.endproc
.proc clevel_irq
; Is C level interrupt request vector set?
lda irqvec+2 ; High byte is enough
bne @L1
clc ; Interrupt not handled
rts
; Save our zero page locations
@L1: ldx #.sizeof(::zpsave)-1
@L2: lda <__ZP_START__,x
sta zpsave,x
dex
bpl @L2
; Save jmpvec
lda jmpvec+1
pha
lda jmpvec+2
pha
; Set C level interrupt stack
lda irqsp
ldx irqsp+1
sta sp
stx sp+1
; Call C level interrupt request handler
jsr irqvec
; Mark interrupt handled / not handled
lsr
; Restore our zero page content
ldx #.sizeof(::zpsave)-1
@L3: lda zpsave,x
sta <__ZP_START__,x
dex
bpl @L3
; Restore jmpvec and return
pla
sta jmpvec+2
pla
sta jmpvec+1
rts
.endproc
|
