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gbdk-2020

GameBoy Development Kit
download: https://git.y1.nz/archives/gbdk.tar.gz
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gbdk-lib/libc/targets/z80/sms_refresh_oam.s

      1         .include        "global.s"
      2 
      3         .title  "VRAM utilities"
      4         .module VRAMUtils
      5 
      6         .globl __shadow_OAM_base
      7 
      8         .ez80
      9 
     10         .area   _HOME
     11 
     12 ; void refresh_OAM();
     13 _refresh_OAM::
     14         DISABLE_VBLANK_COPY     ; switch OFF copy shadow SAT
     15 
     16         ld a, (_shadow_VDP_R5)
     17         srl a
     18         ld d, a
     19         ld e, #0
     20         VDP_WRITE_CMD d, e
     21 
     22         ld h, #>_shadow_OAM
     23         ld l, #0
     24         ld c, #.VDP_DATA
     25         ld b, #64
     26 1$:
     27         outi
     28         jp nz, 1$
     29 
     30         ld e, #0x80
     31         VDP_WRITE_CMD d, e
     32         ld b, #128
     33 2$:
     34         outi
     35         jp nz, 2$
     36 
     37         ENABLE_VBLANK_COPY      ; switch OFF copy shadow SAT
     38         ret

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