mirror of https://github.com/RevCurtisP/C02.git
75 lines
1.5 KiB
Plaintext
75 lines
1.5 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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/* Generate Vertical Sync Signal */
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void vtsync() {
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A=2; //Set Bit 2 (D1)
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WSYNC; //Wait for end of Scanline
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VSYNC=A; //Turn On Vertical Sync
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WSYNC; //Wait 2 More Scanlines
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WSYNC;
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A=0; //Clear Bit 2 (D1)
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WSYNC; //Wait for End of 3rd Scanline
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VSYNC=A; //Turn On Vertical Sync
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}
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/* Execute Vertical Blank Code */
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void vtblnk() {
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X=37; //Delay 37 Scanlines
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do {
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WSYNC; //Wait for end of Scanline
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X--;
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} while (*);
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}
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/* Execute Kernel Code */
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void kernel() {
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A=0; //Clear All Bits
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WSYNC; //Wait for end of Scanline
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VBLANK=A; //Turn Off Vertical Blank
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X=0; //Draw 192 Scanlines (256-64)
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do {
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if (X & 3) {
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WSYNC; //Wait for end of Scanline
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COLUBK = X; //Set Background Color
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}
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X--;
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} while (*);
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}
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/* Execute Overscan Code */
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void ovrscn() {
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WSYNC; //Wait for end of Scanline
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VBLANK=2; //Turn On Vertical Blank
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X=27; //Delay 27 Scanlines
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do {
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WSYNC; //Wait for end of Scanline
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X--;
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} while(*);
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}
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start:
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asm("","SEI","");
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asm("","CLD","");
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A = 0;
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X = A;
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Y = A;
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do {
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X--;
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asm("","TXS","");
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push A;
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} while (*);
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irqbrk: //Code to Execute when BRK Instruction is Encountered
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main: //Start of Program Code
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vtsync(); //Generate Vertical Sync Signal
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vtblnk(); //Generate Vertical Blank Signal
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kernel(); //Execute Kernal Code
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ovrscn(); //Execute Overscan Code
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goto main;
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#include <vcsfoot.h02> //Finalization Code
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