mirror of https://github.com/cc65/cc65.git
120 lines
2.4 KiB
ArmAsm
120 lines
2.4 KiB
ArmAsm
;
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; 2012-01-18, Oliver Schmidt
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; 2015-08-22, Greg King
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;
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; void __fastcall__ set_irq (irq_handler f, void *stack_addr, size_t stack_size);
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; void reset_irq (void);
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;
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.export _set_irq, _reset_irq
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.interruptor clevel_irq, 1 ; Export as low priority IRQ handler
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.import popax, __ZP_START__, jmpvec
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.include "zeropage.inc"
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.macpack generic
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; ---------------------------------------------------------------------------
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.data
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irqvec: jmp $00FF ; Patched at runtime
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; ---------------------------------------------------------------------------
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.bss
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irqsp: .res 2
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zpsave: .res zpsavespace
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; ---------------------------------------------------------------------------
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.code
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.proc _set_irq
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; Keep clevel_irq from being called right now
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sei
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; Set irq stack pointer to stack_addr + stack_size
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sta irqsp
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stx irqsp+1
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jsr popax
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add irqsp
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sta irqsp
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txa
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adc irqsp+1
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sta irqsp+1
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; Set irq vector to irq_handler
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jsr popax
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sta irqvec+1
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stx irqvec+2 ; Set the user vector
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; Restore interrupt requests and return
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cli
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rts
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.endproc
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.proc _reset_irq
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lda #$00
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sta irqvec+2 ; High byte is enough
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rts
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.endproc
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.proc clevel_irq
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; Is C level interrupt request vector set?
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lda irqvec+2 ; High byte is enough
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bne @L1
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clc ; Interrupt not handled
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rts
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; Save our zero page locations
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@L1: ldx #.sizeof(::zpsave)-1
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@L2: lda <__ZP_START__,x
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sta zpsave,x
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dex
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bpl @L2
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; Save jmpvec
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lda jmpvec+1
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pha
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lda jmpvec+2
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pha
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; Set C level interrupt stack
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lda irqsp
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ldx irqsp+1
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sta sp
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stx sp+1
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; Call C level interrupt request handler
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jsr irqvec
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; Mark interrupt handled / not handled
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lsr
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; Restore our zero page content
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ldx #.sizeof(::zpsave)-1
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@L3: lda zpsave,x
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sta <__ZP_START__,x
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dex
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bpl @L3
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; Restore jmpvec and return
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pla
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sta jmpvec+2
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pla
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sta jmpvec+1
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rts
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.endproc
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