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C02/vcs/colorbar.c02
2018-01-28 14:44:10 -05:00

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