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103 lines
1.9 KiB
ArmAsm
103 lines
1.9 KiB
ArmAsm
; Various Common Routines
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; Called the Super-VMW Graphics Library for various sentimental reasons
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.segment "STARTUP"
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;====================================
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; Move Sprites Offscreen
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;====================================
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svmw_move_sprites_offscreen:
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php ; store status on stack
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rep #$30 ; 16bit mem/A, 16 bit X/Y
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.a16
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.i16
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ldx #$0000 ; offset
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lda #$0001
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; OAM format. Low part is:
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; Format is xxxxxxx yyyyyyy cccccccc vhoopppN
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; Upper part is X/Y packed
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; Xxxxxxxxx = X pos
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; Yyyyyyyyy = Y pos
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; cccccccc = first tile of sprite
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; v/h = vert/horiz flip
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; oo = sprite priority
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; ppp = palette
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; s = sprite size
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clear_xy:
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sta $0000,X ; page 0?
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inx
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inx
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inx
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inx ; skip 4 bytes
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cpx #$0200 ; are we 512 bytes yet? (bottom part of OAM)
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bne clear_xy
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ldx #$0000
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lda #$5555 ; set high bit of X, effective setting X to 256
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set_top:
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sta $0200, X ; writing to top of screen
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inx ; increment
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inx
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cpx #$0020 ; put all 32 values
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bne set_top
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plp
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;=====================================
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; transfer sprite
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; assumes sprite_data starts at $7e:0000
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;=====================================
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svmw_transfer_sprite:
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php ; save status word
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rep #$10 ; 16 bit X/Y
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.i16
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sep #$20 ; 8 bit A
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.a8
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; p------b p=special object priority
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; aaaaaaaa baaaaaaaa = OAM address
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stz $2102 ; set OAM address to 0
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stz $2103
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; setup DMA transfer
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; $4300
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; da-ifttt d=direction 0 CPU->PPU 1 PPU->CPU
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; a = HDMA address mode
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; i = DMA address increment 0=+1 1=-1
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; f = fixed transfer 1=no inc, 0=increment
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; ttt = transfer mode
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; $4301
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; pppppppp destination register $2100
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ldy #$0400
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sty $4300 ; CPU -> PPU, auto increment,
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; write 1 reg, $2104 (OAM Write)
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stz $4302
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stz $4303 ; source offset in RAM (low/high)
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; $0000
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ldy #$0220
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sty $4305 ; number of bytes to transfer
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lda #$7E
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sta $4304 ; bank address = $7E (work RAM)
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lda #$01
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sta $420B ; start DMA transfer channel 0
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plp ; restore status word
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rts
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