ReC98/th01/hardware/vsync.c

/* ReC98
 * -----
 * VSync interrupt handler
 */

#include "th01/th01.h"
#include "th01/hardware/vsync.h"

#pragma option -2
#pragma warn -aus

extern char vsync_initialized;
extern int vsync_callback_is_set;

extern int RES_X_HALF;
extern int RES_Y_HALF;

extern int vsync_unused;
extern void interrupt (*vsync_callback_old)(void);
extern void (*vsync_callback)(void);

static void interrupt vsync_intfunc(void)
{
	int res_x_half = RES_X_HALF;
	int res_y_half = RES_Y_HALF;
	vsync_frame++;
	vsync_unused++;
	if(vsync_callback_is_set) {
		vsync_callback();
	}
	OUTB(0x00, 0x20); // End of Interrupt
	OUTB(0x64, 0); // VSync interrupt trigger
}

void vsync_init(void)
{
	if(vsync_initialized == 0) {
		vsync_initialized = 1;
		disable();
		vsync_callback_old = getvect(0x0A);
		setvect(0x0A, vsync_intfunc);

		// Disable all interrupts from 0x08 to 0x0F except for 0x0A
		OUTB(0x02, INPB(0x02) & 0xFB);

		OUTB(0x64, 0); // VSync interrupt trigger
		enable();
	}
}

void vsync_exit(void)
{
	if(vsync_initialized == 1) {
		vsync_initialized = 0;
		disable();

		// Reenable all interrupts from 0x08 to 0x0F except for 0x0A
		OUTB(0x02, INPB(0x02) | 0x04);

		setvect(0x0a, vsync_callback_old);
		enable();
	}
}

void z_vsync_wait(void)
{
	do {
		_AL = INPB(0x60);
	} while((_AL & 0x20) != 0);
	do {
		_AL = INPB(0x60);
	} while((_AL & 0x20) == 0);
}

void vsync_callback_set(void (*vsync_callback_new)())
{
	vsync_callback_is_set = 0;
	vsync_callback = vsync_callback_new;
	vsync_callback_is_set = 1;
}