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