/*ICS2595 clock chip emulation
  Used by ATI Mach64*/

#include "ibm.h"
#include "vid_ics2595.h"

enum {
	ICS2595_IDLE = 0,
	ICS2595_WRITE,
	ICS2595_READ
};

static int ics2595_div[4] = {8, 4, 2, 1};

void ics2595_write(ics2595_t *ics2595, int strobe, int dat) {
//        pclog("ics2595_write : %i %i\n", strobe, dat);
	if (strobe) {
		if ((dat & 8) && !ics2595->oldfs3) /*Data clock*/
		{
//                        pclog(" - new dat %i\n", dat & 4);
			switch (ics2595->state) {
			case ICS2595_IDLE:ics2595->state = (dat & 4) ? ICS2595_WRITE : ICS2595_IDLE;
				ics2595->pos = 0;
				break;
			case ICS2595_WRITE:ics2595->dat = (ics2595->dat >> 1);
				if (dat & 4)
					ics2595->dat |= (1 << 19);
				ics2595->pos++;
				if (ics2595->pos == 20) {
					int d, n, l;
//                                        pclog("ICS2595_WRITE : dat %08X\n", ics2595->dat);
					l = (ics2595->dat >> 2) & 0xf;
					n = ((ics2595->dat >> 7) & 255) + 257;
					d = ics2595_div[(ics2595->dat >> 16) & 3];

					ics2595->clocks[l] = (14318181.8 * ((double)n / 46.0)) / (double)d;
//                                        pclog("ICS2595 clock set - L %i N %i D %i freq = %f\n", l, n, d, (14318181.8 * ((double)n / 46.0)) / (double)d);
					ics2595->state = ICS2595_IDLE;
				}
				break;
			}
		}

		ics2595->oldfs2 = dat & 4;
		ics2595->oldfs3 = dat & 8;
	}
	ics2595->output_clock = ics2595->clocks[dat];
}
