// license:BSD-3-Clause
// copyright-holders:Aaron Giles
/***************************************************************************
Atari Crystal Castles hardware
***************************************************************************/
#include "emu.h"
#include "includes/ccastles.h"
#include "video/resnet.h"
/*************************************
*
* Video startup
*
*************************************/
void ccastles_state::video_start()
{
static const int resistances[3] = { 22000, 10000, 4700 };
/* get pointers to our PROMs */
m_syncprom = memregion("proms")->base() + 0x000;
m_wpprom = memregion("proms")->base() + 0x200;
m_priprom = memregion("proms")->base() + 0x300;
/* compute the color output resistor weights at startup */
compute_resistor_weights(0, 255, -1.0,
3, resistances, m_rweights, 1000, 0,
3, resistances, m_gweights, 1000, 0,
3, resistances, m_bweights, 1000, 0);
/* allocate a bitmap for drawing sprites */
m_screen->register_screen_bitmap(m_spritebitmap);
/* register for savestates */
save_item(NAME(m_bitmode_addr));
save_item(NAME(m_hscroll));
save_item(NAME(m_vscroll));
}
/*************************************
*
* Video control registers
*
*************************************/
WRITE8_MEMBER(ccastles_state::ccastles_hscroll_w)
{
m_screen->update_partial(m_screen->vpos());
m_hscroll = data;
}
WRITE8_MEMBER(ccastles_state::ccastles_vscroll_w)
{
m_vscroll = data;
}
WRITE8_MEMBER(ccastles_state::ccastles_video_control_w)
{
/* only D3 matters */
m_outlatch[1]->write_bit(offset, BIT(data, 3));
}
/*************************************
*
* Palette RAM accesses
*
*************************************/
WRITE8_MEMBER(ccastles_state::ccastles_paletteram_w)
{
int bit0, bit1, bit2;
int r, g, b;
/* extract the raw RGB bits */
r = ((data & 0xc0) >> 6) | ((offset & 0x20) >> 3);
b = (data & 0x38) >> 3;
g = (data & 0x07);
/* red component (inverted) */
bit0 = (~r >> 0) & 0x01;
bit1 = (~r >> 1) & 0x01;
bit2 = (~r >> 2) & 0x01;
r = combine_weights(m_rweights, bit0, bit1, bit2);
/* green component (inverted) */
bit0 = (~g >> 0) & 0x01;
bit1 = (~g >> 1) & 0x01;
bit2 = (~g >> 2) & 0x01;
g = combine_weights(m_gweights, bit0, bit1, bit2);
/* blue component (inverted) */
bit0 = (~b >> 0) & 0x01;
bit1 = (~b >> 1) & 0x01;
bit2 = (~b >> 2) & 0x01;
b = combine_weights(m_bweights, bit0, bit1, bit2);
m_palette->set_pen_color(offset & 0x1f, rgb_t(r, g, b));
}
/*************************************
*
* Video RAM access via the write
* protect PROM
*
*************************************/
inline void ccastles_state::ccastles_write_vram( uint16_t addr, uint8_t data, uint8_t bitmd, uint8_t pixba )
{
uint8_t *dest = &m_videoram[addr & 0x7ffe];
uint8_t promaddr = 0;
uint8_t wpbits;
/*
Inputs to the write-protect PROM:
Bit 7 = BA1520 = 0 if (BA15-BA12 != 0), or 1 otherwise
Bit 6 = DRBA11
Bit 5 = DRBA10
Bit 4 = /BITMD
Bit 3 = GND
Bit 2 = BA0
Bit 1 = PIXB
Bit 0 = PIXA
*/
promaddr |= ((addr & 0xf000) == 0) << 7;
promaddr |= (addr & 0x0c00) >> 5;
promaddr |= (!bitmd) << 4;
promaddr |= (addr & 0x0001) << 2;
promaddr |= (pixba << 0);
/* look up the PROM result */
wpbits = m_wpprom[promaddr];
/* write to the appropriate parts of VRAM depending on the result */
if (!(wpbits & 1))
dest[0] = (dest[0] & 0xf0) | (data & 0x0f);
if (!(wpbits & 2))
dest[0] = (dest[0] & 0x0f) | (data & 0xf0);
if (!(wpbits & 4))
dest[1] = (dest[1] & 0xf0) | (data & 0x0f);
if (!(wpbits & 8))
dest[1] = (dest[1] & 0x0f) | (data & 0xf0);
}
/*************************************
*
* Autoincrement control for bit mode
*
*************************************/
inline void ccastles_state::bitmode_autoinc( )
{
/* auto increment in the x-direction if it's enabled */
if (!m_outlatch[1]->q0_r()) /* /AX */
{
if (!m_outlatch[1]->q2_r()) /* /XINC */
m_bitmode_addr[0]++;
else
m_bitmode_addr[0]--;
}
/* auto increment in the y-direction if it's enabled */
if (!m_outlatch[1]->q1_r()) /* /AY */
{
if (!m_outlatch[1]->q3_r()) /* /YINC */
m_bitmode_addr[1]++;
else
m_bitmode_addr[1]--;
}
}
/*************************************
*
* Standard video RAM access
*
*************************************/
WRITE8_MEMBER(ccastles_state::ccastles_videoram_w)
{
/* direct writes to VRAM go through the write protect PROM as well */
ccastles_write_vram(offset, data, 0, 0);
}
/*************************************
*
* Bit mode video RAM access
*
*************************************/
READ8_MEMBER(ccastles_state::ccastles_bitmode_r)
{
/* in bitmode, the address comes from the autoincrement latches */
uint16_t addr = (m_bitmode_addr[1] << 7) | (m_bitmode_addr[0] >> 1);
/* the appropriate pixel is selected into the upper 4 bits */
uint8_t result = m_videoram[addr] << ((~m_bitmode_addr[0] & 1) * 4);
/* autoincrement because /BITMD was selected */
bitmode_autoinc();
/* the low 4 bits of the data lines are not driven so make them all 1's */
return result | 0x0f;
}
WRITE8_MEMBER(ccastles_state::ccastles_bitmode_w)
{
/* in bitmode, the address comes from the autoincrement latches */
uint16_t addr = (m_bitmode_addr[1] << 7) | (m_bitmode_addr[0] >> 1);
/* the upper 4 bits of data are replicated to the lower 4 bits */
data = (data & 0xf0) | (data >> 4);
/* write through the generic VRAM routine, passing the low 2 X bits as PIXB/PIXA */
ccastles_write_vram(addr, data, 1, m_bitmode_addr[0] & 3);
/* autoincrement because /BITMD was selected */
bitmode_autoinc();
}
WRITE8_MEMBER(ccastles_state::ccastles_bitmode_addr_w)
{
/* write through to video RAM and also to the addressing latches */
ccastles_write_vram(offset, data, 0, 0);
m_bitmode_addr[offset] = data;
}
/*************************************
*
* Video updating
*
*************************************/
uint32_t ccastles_state::screen_update_ccastles(screen_device &screen, bitmap_ind16 &bitmap, const rectangle &cliprect)
{
uint8_t *spriteaddr = &m_spriteram[m_outlatch[1]->q7_r() * 0x100]; /* BUF1/BUF2 */
int flip = m_outlatch[1]->q4_r() ? 0xff : 0x00; /* PLAYER2 */
pen_t black = m_palette->black_pen();
int x, y, offs;
/* draw the sprites */
m_spritebitmap.fill(0x0f, cliprect);
for (offs = 0; offs < 320/2; offs += 4)
{
int x = spriteaddr[offs + 3];
int y = 256 - 16 - spriteaddr[offs + 1];
int which = spriteaddr[offs];
int color = spriteaddr[offs + 2] >> 7;
m_gfxdecode->gfx(0)->transpen(m_spritebitmap,cliprect, which, color, flip, flip, x, y, 7);
}
/* draw the bitmap to the screen, looping over Y */
for (y = cliprect.top(); y <= cliprect.bottom(); y++)
{
uint16_t *dst = &bitmap.pix16(y);
/* if we're in the VBLANK region, just fill with black */
if (m_syncprom[y] & 1)
{
for (x = cliprect.left(); x <= cliprect.right(); x++)
dst[x] = black;
}
/* non-VBLANK region: merge the sprites and the bitmap */
else
{
uint16_t *mosrc = &m_spritebitmap.pix16(y);
int effy = (((y - m_vblank_end) + (flip ? 0 : m_vscroll)) ^ flip) & 0xff;
uint8_t *src;
/* the "POTATO" chip does some magic here; this is just a guess */
if (effy < 24)
effy = 24;
src = &m_videoram[effy * 128];
/* loop over X */
for (x = cliprect.left(); x <= cliprect.right(); x++)
{
/* if we're in the HBLANK region, just store black */
if (x >= 256)
dst[x] = black;
/* otherwise, process normally */
else
{
int effx = (m_hscroll + (x ^ flip)) & 255;
/* low 4 bits = left pixel, high 4 bits = right pixel */
uint8_t pix = (src[effx / 2] >> ((effx & 1) * 4)) & 0x0f;
uint8_t mopix = mosrc[x];
uint8_t prindex, prvalue;
/* Inputs to the priority PROM:
Bit 7 = GND
Bit 6 = /CRAM
Bit 5 = BA4
Bit 4 = MV2
Bit 3 = MV1
Bit 2 = MV0
Bit 1 = MPI
Bit 0 = BIT3
*/
prindex = 0x40;
prindex |= (mopix & 7) << 2;
prindex |= (mopix & 8) >> 2;
prindex |= (pix & 8) >> 3;
prvalue = m_priprom[prindex];
/* Bit 1 of prvalue selects the low 4 bits of the final pixel */
if (prvalue & 2)
pix = mopix;
/* Bit 0 of prvalue selects bit 4 of the final color */
pix |= (prvalue & 1) << 4;
/* store the pixel value and also a priority value based on the topmost bit */
dst[x] = pix;
}
}
}
}
return 0;
}