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AmigActive 10
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vidhrdw
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qix.c
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C/C++ Source or Header
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2000-04-04
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6KB
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232 lines
/***************************************************************************
vidhrdw.c
Functions to emulate the video hardware of the machine.
***************************************************************************/
#include "driver.h"
#include "vidhrdw/generic.h"
unsigned char *qix_palettebank;
unsigned char *qix_videoaddress;
/*#define DEBUG_LEDS*/
#ifdef DEBUG_LEDS
#include <stdio.h>
static FILE *led_log;
#endif
/***************************************************************************
Convert the color PROMs into a more useable format.
Qix doesn't have colors PROMs, it uses RAM. The meaning of the bits are
bit 7 -- Red
-- Red
-- Green
-- Green
-- Blue
-- Blue
-- Intensity
bit 0 -- Intensity
***************************************************************************/
static void update_pen (int pen, int val)
{
/* this conversion table should be about right. It gives a reasonable */
/* gray scale in the test screen, and the red, green and blue squares */
/* in the same screen are barely visible, as the manual requires. */
static unsigned char table[16] =
{
0x00, /* value = 0, intensity = 0 */
0x12, /* value = 0, intensity = 1 */
0x24, /* value = 0, intensity = 2 */
0x49, /* value = 0, intensity = 3 */
0x12, /* value = 1, intensity = 0 */
0x24, /* value = 1, intensity = 1 */
0x49, /* value = 1, intensity = 2 */
0x92, /* value = 1, intensity = 3 */
0x5b, /* value = 2, intensity = 0 */
0x6d, /* value = 2, intensity = 1 */
0x92, /* value = 2, intensity = 2 */
0xdb, /* value = 2, intensity = 3 */
0x7f, /* value = 3, intensity = 0 */
0x91, /* value = 3, intensity = 1 */
0xb6, /* value = 3, intensity = 2 */
0xff /* value = 3, intensity = 3 */
};
int bits,intensity,red,green,blue;
intensity = (val >> 0) & 0x03;
bits = (val >> 6) & 0x03;
red = table[(bits << 2) | intensity];
bits = (val >> 4) & 0x03;
green = table[(bits << 2) | intensity];
bits = (val >> 2) & 0x03;
blue = table[(bits << 2) | intensity];
palette_change_color(pen,red,green,blue);
}
/***************************************************************************
Start the video hardware emulation.
***************************************************************************/
int qix_vh_start(void)
{
if ((videoram = malloc(256*256)) == 0)
return 1;
#ifdef DEBUG_LEDS
led_log = fopen ("led.log","w");
#endif
return 0;
}
/***************************************************************************
Stop the video hardware emulation.
***************************************************************************/
void qix_vh_stop(void)
{
free (videoram);
videoram = 0;
#ifdef DEBUG_LEDS
if (led_log) fclose (led_log);
led_log = 0;
#endif
}
/* The screen is 256x256 with eight bit pixels (64K). The screen is divided
into two halves each half mapped by the video CPU at $0000-$7FFF. The
high order bit of the address latch at $9402 specifies which half of the
screen is being accessed.
The address latch works as follows. When the video CPU accesses $9400,
the screen address is computed by using the values at $9402 (high byte)
and $9403 (low byte) to get a value between $0000-$FFFF. The value at
that location is either returned or written. */
READ_HANDLER( qix_videoram_r )
{
offset += (qix_videoaddress[0] & 0x80) * 0x100;
return videoram[offset];
}
WRITE_HANDLER( qix_videoram_w )
{
int x, y;
offset += (qix_videoaddress[0] & 0x80) * 0x100;
x = offset & 0xff;
y = offset >> 8;
plot_pixel(Machine->scrbitmap, x, y, Machine->pens[data]);
videoram[offset] = data;
}
READ_HANDLER( qix_addresslatch_r )
{
offset = qix_videoaddress[0] * 0x100 + qix_videoaddress[1];
return videoram[offset];
}
WRITE_HANDLER( qix_addresslatch_w )
{
int x, y;
offset = qix_videoaddress[0] * 0x100 + qix_videoaddress[1];
x = offset & 0xff;
y = offset >> 8;
plot_pixel(Machine->scrbitmap, x, y, Machine->pens[data]);
videoram[offset] = data;
}
/* The color RAM works as follows. The color RAM contains palette values for
four pages (0-3). When a write to $8800 on the video CPU occurs, the color
RAM page is taken from the lowest 2 bits of the value. This selects one of
the color RAM pages as follows:
colorRAMAddr = 0x9000 + ((data & 0x03) * 0x100);
Qix uses a palette of 64 colors (2 each RGB) and four intensities (RRGGBBII).
*/
WRITE_HANDLER( qix_paletteram_w )
{
paletteram[offset] = data;
if ((*qix_palettebank & 0x03) == (offset / 256))
update_pen (offset % 256, data);
}
WRITE_HANDLER( qix_palettebank_w )
{
if ((*qix_palettebank & 0x03) != (data & 0x03))
{
unsigned char *pram = &paletteram[256 * (data & 0x03)];
int i;
for (i = 0;i < 256;i++)
update_pen (i, *pram++);
}
*qix_palettebank = data;
#ifdef DEBUG_LEDS
data = ~(data) & 0xfc;
if (led_log)
{
fprintf (led_log, "LEDS: %d %d %d %d %d %d\n", (data & 0x80)>>7, (data & 0x40)>>6,
(data & 0x20)>>5, (data & 0x10)>>4, (data & 0x08)>>3, (data & 0x04)>>2 );
}
#endif
}
void qix_vh_screenrefresh(struct osd_bitmap *bitmap,int full_refresh)
{
/* recalc the palette if necessary */
if (palette_recalc () || full_refresh)
{
int offs;
for (offs = 0; offs < 256*256; offs++)
{
int x = offs & 0xff;
int y = offs >> 8;
plot_pixel(bitmap, x, y, Machine->pens[videoram[offs]]);
}
}
}