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C02/vcs/include/colors.a02

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;colors.a02 - Atari 2600 Color/BW Assembly Language Routines
;getclr(mask, clr, bw) - Get Color Based on Color B&W Switch Position
;Args: A - Mask for Color Cycling (0=None)
; Y - Color/Luminance to use in Color Mode
; X - Color/Luminance to use in B&W Mode
;Returns: Color to Use
GETCLR: STA TEMP2 ;Save Color Cycling Mask
LDA SWCHB ;Read Console Switches
AND #%00001000 ;Test TV Type Switch
BNE GETCLC ;If Off
TXA ; Load B&W Mode Color/Luminance
EOR TEMP2 ; Apply Mask
AND #$0F ; and Strip High Nybble
RTS ;Else
GETCLC: TYA ; Load Color Mode Color/Luminance
EOR TEMP2 ; and Apply Apply Mask
RTS ;Return Selected Color
;setclr(mask, &clrtbl) - Set Object Colors
;Args: X,Y = Pointer to 8-Byte Color Table Color Table
; Player0, Player1, Playfield, Background (Color)
; Player0, Player1, Playfield, Background (B&W)
;Sets: TEMP0,TEMP1 = Pointer to Color Table
;Affects: A,X,Y,N,Z
SETCLR: STY TEMP1 ;Save Pointer to Color Table
STX TEMP0
STA TEMP2 ;Save Color Cycling Mask
LDX #3 ;Setting 4 colors (0-3)
LDY #3 ;Refault to the color entries in the table (0-3)
LDA SWCHB ;Read Console Switches
AND #%00001000 ;Test TV Type Switch
BNE SETCLL ;If On
LDA #$0F ; Use Color Entries
AND TEMP2 ;Else
STA TEMP2 ; Strip High Nybble from Mask
LDY #7 ; and Use B&W Entries
SETCLL: LDA (TEMP0),Y ;Get Color/B&W Value
EOR TEMP2 ;Apply Color Cycling Mask
STA COLUP0,x ;and Set Object Color
DEY ;Decrement Table Pointer
DEX ;Decrement Register Pointer
BPL SETCLL ;If >0, Loop
RTS ;Return