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51 lines
1.0 KiB
Plaintext
51 lines
1.0 KiB
Plaintext
/* Atari VCS Color Bars Program */
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#pragma origin $F800 //2k Cartridge
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#include <vcshead.h02> //TIA and RIOT Registers
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#include <vcsstub.h02> //Initialize VCS
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zeropage char clrbkg; //Background Color
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zeropage char clrmov; //Color Movement Flag
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zeropage char clrofs; //Color Offset
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zeropage char clrmsk; //Color/B&W Mask
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/* Setup Code */
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void setup() {
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return;
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}
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/* Vertical Blank Code */
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void vrtblk() {
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return;
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}
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/* Execute Kernel Code */
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void kernel() {
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X=192; //Draw 192 Scanlines
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do {
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clrbkg = X;
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if (!SWCHB & 128) clrbkg<<;
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A = clrbkg + clrofs & clrmsk; //Set Background Color
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WSYNC = A; //Wait for end of Scanline
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COLUBK = A; //Set Background Color
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X--;
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} while (X);
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return;
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}
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/* Execute Overscan Code */
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void ovrscn() {
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if (!SWCHB & 1) //Game Reset
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clrmov = $FF; //Turn On Scrolling
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if (!SWCHB & 2) //Game Select
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clrmov = 0; //Turn Off Scrolling
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clrmsk = (SWCHB & 8) ? $FF : $0F;
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if (clrmov) {
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if (SWCHB & 64) clrofs--; else clrofs++;
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}
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}
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#include <vcsfoot.h02> //Finalization Code
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