dmgtris/src/interrupts.asm

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IF !DEF(INTERRUPTS_ASM)
DEF INTERRUPTS_ASM EQU 1
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INCLUDE "globals.asm"
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SECTION "Interrupt Variables", HRAM
hLCDCCtr:: ds 1
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SECTION "Interrupt Initialization Functions", ROM0
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IntrInit::
xor a, a
ldh [hLCDCCtr], a
ret
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InitializeLCDCInterrupt::
ld a, STATF_LYC
ldh [rSTAT], a
ld a, 6
ldh [rLYC], a
ld a, 0
ldh [rSCY], a
ld a, IEF_STAT
ldh [rIE], a
xor a, a
ldh [rIF], a
ei
ret
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SECTION "LCDC Interrupt", ROM0[INT_HANDLER_STAT]
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LCDCInterrupt:
push af
push hl
ld hl, rSTAT
LCDCInterrupt_WaitUntilNotBusy:
bit STATB_BUSY, [hl]
jr nz, LCDCInterrupt_WaitUntilNotBusy
; Increment SCY
ldh a, [rSCY]
inc a
ldh [rSCY], a
; Increment LYC by 7
ldh a, [rLYC]
add a, 7
ldh [rLYC], a
; Check our interrupt counter
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ldh a, [hLCDCCtr]
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cp 21
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jr nz, LCDCInterrupt_End
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ld a, 255
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ldh [hLCDCCtr], a
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ld a, 6
ldh [rLYC], a
ld a, 0
ldh [rSCY], a
LCDCInterrupt_End:
inc a
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ldh [hLCDCCtr], a
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pop hl
pop af
reti
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ENDC