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57 lines
1.9 KiB
C
57 lines
1.9 KiB
C
/*****************************************************************************/
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/* */
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/* Atari VCS 2600 sample C program */
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/* */
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/* Florent Flament (contact@florentflament.com), 2017 */
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/* */
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/*****************************************************************************/
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#include <atari2600.h>
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// PAL Timings
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// Roughly computed based on Stella Programmer's guide (Steve Wright)
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// scanlines count per section.
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#define VBLANK_TIM64 51 // 45 lines * 76 cycles/line / 64 cycles/tick
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#define KERNAL_T1024 17 // 228 lines * 76 cycles/line / 1024 cycles/tick
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#define OVERSCAN_TIM64 42 // 36 lines * 76 cycles/line / 64 cycles/tick
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// Testing memory zones
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const unsigned char rodata_v[] = "Hello!";
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unsigned char data_v = 0x77;
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unsigned char bss_v;
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void main(void) {
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unsigned char color = 0x79; // Stack variable
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bss_v = 0x88; // Testing BSS variable
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for/*ever*/(;;) {
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// Vertical Sync signal
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TIA.vsync = 0x02;
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TIA.wsync = 0x00;
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TIA.wsync = 0x00;
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TIA.wsync = 0x00;
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TIA.vsync = 0x00;
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// Vertical Blank timer setting
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RIOT.tim64t = VBLANK_TIM64;
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// Doing frame computation during blank
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TIA.colubk = color++; // Update color
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// Wait for end of Vertical Blank
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while (RIOT.timint == 0) {}
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TIA.wsync = 0x00;
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TIA.vblank = 0x00; // Turn on beam
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// Display frame
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RIOT.t1024t = KERNAL_T1024;
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while (RIOT.timint == 0) {}
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TIA.wsync = 0x00;
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TIA.vblank = 0x02; // Turn off beam
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// Overscan
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RIOT.tim64t = OVERSCAN_TIM64;
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while (RIOT.timint == 0) {}
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}
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}
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