86Box/src/video/vid_ics2595.c

/*
 * 86Box	A hypervisor and IBM PC system emulator that specializes in
 *		running old operating systems and software designed for IBM
 *		PC systems and compatibles from 1981 through fairly recent
 *		system designs based on the PCI bus.
 *
 *		This file is part of the 86Box distribution.
 *
 *		ICS2595 clock chip emulation.  Used by ATI Mach64.
 *
 *
 *
 * Authors:	Sarah Walker, <http://pcem-emulator.co.uk/>
 *		Miran Grca, <mgrca8@gmail.com>
 *
 *		Copyright 2008-2018 Sarah Walker.
 *		Copyright 2016-2018 Miran Grca.
 */
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>
#include <86box/86box.h>
#include <86box/device.h>


typedef struct ics2595_t
{
    int oldfs3, oldfs2;
    int dat;
    int pos, state;

    double clocks[16];
    double output_clock;
} ics2595_t;


enum
{
        ICS2595_IDLE = 0,
        ICS2595_WRITE,
        ICS2595_READ
};


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


void
ics2595_write(void *p, int strobe, int dat)
{
    ics2595_t *ics2595 = (ics2595_t *) p;
    int d, n;
    int l;

    if (strobe) {
	if ((dat & 8) && !ics2595->oldfs3) {	/*Data clock*/
		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) {
					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;
					ics2595->state = ICS2595_IDLE;
				}
				break;                                                
		}
	}

	ics2595->oldfs2 = dat & 4;
	ics2595->oldfs3 = dat & 8;
    }

    ics2595->output_clock = ics2595->clocks[dat];
}


static void *
ics2595_init(const device_t *info)
{
    ics2595_t *ics2595 = (ics2595_t *) malloc(sizeof(ics2595_t));
    memset(ics2595, 0, sizeof(ics2595_t));

    return ics2595;
}


static void
ics2595_close(void *priv)
{
    ics2595_t *ics2595 = (ics2595_t *) priv;

    if (ics2595)
	free(ics2595);
}


double
ics2595_getclock(void *p)
{
    ics2595_t *ics2595 = (ics2595_t *) p;

    return ics2595->output_clock;
}


void
ics2595_setclock(void *p, double clock)
{
    ics2595_t *ics2595 = (ics2595_t *) p;

    ics2595->output_clock = clock;
}


const device_t ics2595_device =
{
        "ICS2595 clock chip",
        0, 0,
        ics2595_init, ics2595_close,
	NULL, { NULL }, NULL, NULL
};