mirror of
https://github.com/cc65/cc65.git
synced 2024-12-23 19:29:37 +00:00
57 lines
1.7 KiB
C
57 lines
1.7 KiB
C
|
/*****************************************************************************/
|
||
|
|
/* */
|
||
|
|
/* Atari VCS 2600 sample C program */
|
||
|
|
/* */
|
||
|
|
/* Florent Flament (contact@florentflament.com), 2017 */
|
||
|
|
/* */
|
||
|
|
/*****************************************************************************/
|
||
|
|
|
||
|
|
#include <atari2600.h>
|
||
|
|
|
||
|
|
// PAL Timings
|
||
|
|
// Roughly computed based on Stella Programmer's guide (Steve Wright)
|
||
|
|
// scanlines count per section.
|
||
|
|
#define VBLANK_TIM64 51 // 45 lines * 76 cycles/line / 64 cycles/tick
|
||
|
|
#define KERNAL_T1024 17 // 228 lines * 76 cycles/line / 1024 cycles/tick
|
||
|
|
#define OVERSCAN_TIM64 42 // 36 lines * 76 cycles/line / 64 cycles/tick
|
||
|
|
|
||
|
|
// Testing memory zones
|
||
|
|
const unsigned char rodata_v[] = "Hello!";
|
||
|
|
unsigned char data_v = 0x77;
|
||
|
|
unsigned char bss_v;
|
||
|
|
|
||
|
|
void main(void) {
|
||
|
|
unsigned char color = 0x79; // Stack variable
|
||
|
|
bss_v = 0x88; // Testing BSS variable
|
||
|
|
|
||
|
|
for/*ever*/(;;) {
|
||
|
|
// Vertical Sync signal
|
||
|
|
TIA.vsync = 0x02;
|
||
|
|
TIA.wsync = 0x00;
|
||
|
|
TIA.wsync = 0x00;
|
||
|
|
TIA.wsync = 0x00;
|
||
|
|
TIA.vsync = 0x00;
|
||
|
|
|
||
|
|
// Vertical Blank timer setting
|
||
|
|
RIOT.tim64t = VBLANK_TIM64;
|
||
|
|
|
||
|
|
// Doing frame computation during blank
|
||
|
|
TIA.colubk = color++; // Update color
|
||
|
|
|
||
|
|
// Wait for end of Vertical Blank
|
||
|
|
while (RIOT.timint == 0) {}
|
||
|
|
TIA.wsync = 0x00;
|
||
|
|
TIA.vblank = 0x00; // Turn on beam
|
||
|
|
|
||
|
|
// Display frame
|
||
|
|
RIOT.t1024t = KERNAL_T1024;
|
||
|
|
while (RIOT.timint == 0) {}
|
||
|
|
TIA.wsync = 0x00;
|
||
|
|
TIA.vblank = 0x02; // Turn off beam
|
||
|
|
|
||
|
|
// Overscan
|
||
|
|
RIOT.tim64t = OVERSCAN_TIM64;
|
||
|
|
while (RIOT.timint == 0) {}
|
||
|
|
}
|
||
|
|
}
|