island-story/src/oam.s

INCLUDE "hardware.inc"

SECTION "OAM Mirror", WRAM0, ALIGN[8]

_OAM:: ds OAM_COUNT * sizeof_OAM_ATTRS
_OAM_end:

SECTION "OAM Code", ROM0

; Initialize OAM
OAM_Init::
    ; Clear internal OAM
    ld hl, _OAM
    xor a
    ld c, _OAM_end - _OAM
    call memset

    ; Copy DMA transfer routine to HRAM
    ld hl, waitForDMA
    ld bc, DMA_Start
    ld d, waitForDMA_end - waitForDMA
    call memcpy

    ret

; Wait for DMA transfer from $XX00 to complete (~160 cycles)
; @param a $XX
waitForDMA:
    ld [rDMA], a
    ld a, 40
.wait:
    dec a
    jr nz, .wait
    ret
waitForDMA_end:

SECTION "OAM DMA", HRAM

DMA_Start::
    ds waitForDMA_end - waitForDMA