154 lines
4.4 KiB
ArmAsm
154 lines
4.4 KiB
ArmAsm
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; Graphic screen initialization
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InitGraphics
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jsr _ShadowOn
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jsr _GrafOn
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lda #0
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jsr _ClearToColor
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lda #0
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jsr _SetSCBs
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ldx #DefaultPalette
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lda #0
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jsr _SetPalette
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jsr _InitBG0 ; Initialize the background layers
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jsr _InitBG1
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lda #0
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jsr _ClearBG1Buffer
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rts
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DefaultPalette dw $0000,$007F,$0090,$0FF0
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dw $000F,$0080,$0f70,$0FFF
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dw $0fa9,$0ff0,$00e0,$04DF
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dw $0d00,$078f,$0ccc,$0FFF
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; Return the current border color ($0 - $F) in the accumulator
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_GetBorderColor lda #0000
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sep #$20
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ldal BORDER_REG
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and #$0F
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rep #$20
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rts
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; Set the border color to the accumulator value.
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SetBorderColor ENT
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jsr _SetBorderColor
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rtl
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_SetBorderColor sep #$20 ; ACC = $X_Y, REG = $W_Z
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eorl BORDER_REG ; ACC = $(X^Y)_(Y^Z)
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and #$0F ; ACC = $0_(Y^Z)
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eorl BORDER_REG ; ACC = $W_(Y^Z^Z) = $W_Y
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stal BORDER_REG
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rep #$20
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rts
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; Clear to SHR screen to a specific color
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_ClearToColor
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ldx #$7D00 ;start at top of pixel data! ($2000-9D00)
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:clearloop dex
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dex
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stal SHR_SCREEN,x ;screen location
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bne :clearloop ;loop until we've worked our way down to 0
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rts
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; Set a palette values
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; A = high word of palette data pointer, X = low word of palette data pointer, Y = palette number
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SetPalette ENT
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phb ; save old data bank
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pha ; push 16-bit value
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plb ; pop 8-bit bank register
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tya
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jsr _SetPalette
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plb ; pop the other half og the 16-bit push off
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plb ; restore the original data bank
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rtl
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; A = palette number, X = palette address
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_SetPalette
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and #$000F ; palette values are 0 - 15 and each palette is 32 bytes
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asl
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asl
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asl
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asl
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asl
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txy
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tax
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]idx equ 0
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lup 16
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lda: $0000+]idx,y
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stal SHR_PALETTES+]idx,x
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]idx equ ]idx+2
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--^
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rts
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; Initialize the SCB
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_SetSCBs
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ldx #$0100 ;set all $100 scbs to A
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:scbloop dex
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dex
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stal SHR_SCB,x
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bne :scbloop
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rts
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; Turn SHR screen On/Off
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_GrafOn
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sep #$20
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lda #$81
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stal NEW_VIDEO_REG
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rep #$20
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rts
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_GrafOff
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sep #$20
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lda #$01
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stal NEW_VIDEO_REG
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rep #$20
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rts
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; Enable/Disable Shadowing.
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_ShadowOn
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sep #$20
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ldal SHADOW_REG
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and #$F7
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stal SHADOW_REG
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rep #$20
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rts
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_ShadowOff
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sep #$20
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ldal SHADOW_REG
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ora #$08
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stal SHADOW_REG
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rep #$20
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rts
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_GetVBL
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sep #$20
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ldal VBL_HORZ_REG
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asl
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ldal VBL_VERT_REG
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rol ; put V5 into carry bit, if needed. See TN #39 for details.
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rep #$20
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and #$00FF
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rts
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_WaitForVBL
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sep #$20
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:wait1 ldal VBL_STATE_REG ; If we are already in VBL, then wait
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bmi :wait1
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:wait2 ldal VBL_STATE_REG
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bpl :wait2 ; spin until transition into VBL
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rep #$20
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rts
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