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/*****************************************************************************
*
* video/abc802.c
*
****************************************************************************/
#include "includes/abc80x.h"
// these are needed because the MC6845 emulation does
// not position the active display area correctly
#define HORIZONTAL_PORCH_HACK 121
#define VERTICAL_PORCH_HACK 29
//-------------------------------------------------
// MC6845_UPDATE_ROW( abc802_update_row )
//-------------------------------------------------
static MC6845_UPDATE_ROW( abc802_update_row )
{
/*
PAL16R4 equation:
IF (VCC) *OS = FC + RF / RC
*RG: = HS / *RG + *ATE / *RG + ATD / *RG + LL /
*RG + AT1 / *RG + AT0 / ATE + *ATD + *LL +
*AT1 + *AT0
*RI: = *RI + *INV / *RI + LL / *INV + *LL
*RF: = HS / *RF + *ATE / *RF + ATD / *RF + LL /
*RF + AT1 / *RF + AT0 / ATE + *ATD + *LL +
*AT1 + AT0
*RC: = HS / *RC + *ATE / *RC + *ATD / *RC + LL /
*RC + *ATI / *RC + AT0 / ATE + *LL + *AT1 +
*AT0
IF (VCC) *O0 = *CUR + *AT0 / *CUR + ATE
*O1 = *CUR + *AT1 / *CUR + ATE
+ = AND
/ = OR
* = Inverted
ATD Attribute data
ATE Attribute enable
AT0,AT1 Attribute address
CUR Cursor
FC FLSH clock
HS Horizontal sync
INV Inverted signal input
LL Load when Low
OEL Output Enable when Low
RC Row clear
RF Row flash
RG Row graphic
RI Row inverted
*/
abc802_state *state = device->machine().driver_data<abc802_state>();
int rf = 0, rc = 0, rg = 0;
// prevent wraparound
if (y >= 240) return;
y += VERTICAL_PORCH_HACK;
for (int column = 0; column < x_count; column++)
{
UINT8 code = state->m_char_ram[(ma + column) & 0x7ff];
UINT16 address = code << 4;
UINT8 ra_latch = ra;
UINT8 data;
int ri = (code & ABC802_INV) ? 1 : 0;
if (column == cursor_x)
{
ra_latch = 0x0f;
}
if ((state->m_flshclk && rf) || rc)
{
ra_latch = 0x0e;
}
if (rg)
{
address |= 0x800;
}
data = state->m_char_rom->base()[(address + ra_latch) & 0xfff];
if (data & ABC802_ATE)
{
int attr = data & 0x03;
int value = (data & ABC802_ATD) ? 1 : 0;
switch (attr)
{
case 0x00:
// Row Graphic
rg = value;
break;
case 0x01:
// Row Flash
rf = value;
break;
case 0x02:
// Row Clear
rc = value;
break;
case 0x03:
// undefined
break;
}
}
else
{
data <<= 2;
if (state->m_80_40_mux)
{
for (int bit = 0; bit < ABC800_CHAR_WIDTH; bit++)
{
int x = HORIZONTAL_PORCH_HACK + ((column + 3) * ABC800_CHAR_WIDTH) + bit;
int color = BIT(data, 7) ^ ri;
bitmap.pix32(y, x) = RGB_MONOCHROME_AMBER[color];
data <<= 1;
}
}
else
{
for (int bit = 0; bit < ABC800_CHAR_WIDTH; bit++)
{
int x = HORIZONTAL_PORCH_HACK + ((column + 3) * ABC800_CHAR_WIDTH) + (bit << 1);
int color = BIT(data, 7) ^ ri;
bitmap.pix32(y, x) = RGB_MONOCHROME_AMBER[color];
bitmap.pix32(y, x + 1) = RGB_MONOCHROME_AMBER[color];
data <<= 1;
}
column++;
}
}
}
}
//-------------------------------------------------
// vs_w - vertical sync write
//-------------------------------------------------
WRITE_LINE_MEMBER( abc802_state::vs_w )
{
if (!state)
{
// flash clock
if (m_flshclk_ctr & 0x20)
{
m_flshclk = !m_flshclk;
m_flshclk_ctr = 0;
}
else
{
m_flshclk_ctr++;
}
}
// signal _DEW to DART
m_dart->ri_w(1, !state);
}
//-------------------------------------------------
// mc6845_interface crtc_intf
//-------------------------------------------------
static MC6845_INTERFACE( crtc_intf )
{
SCREEN_TAG,
false,
ABC800_CHAR_WIDTH,
NULL,
abc802_update_row,
NULL,
DEVCB_NULL,
DEVCB_NULL,
DEVCB_NULL,
DEVCB_DRIVER_LINE_MEMBER(abc802_state, vs_w),
NULL
};
//-------------------------------------------------
// VIDEO_START( abc802 )
//-------------------------------------------------
void abc802_state::video_start()
{
// register for state saving
save_item(NAME(m_flshclk_ctr));
save_item(NAME(m_flshclk));
save_item(NAME(m_80_40_mux));
}
//-------------------------------------------------
// SCREEN_UPDATE( abc802 )
//-------------------------------------------------
UINT32 abc802_state::screen_update(screen_device &screen, bitmap_rgb32 &bitmap, const rectangle &cliprect)
{
// HACK expand visible area to workaround MC6845
screen.set_visible_area(0, 767, 0, 311);
// draw text
m_crtc->screen_update(screen, bitmap, cliprect);
return 0;
}
//-------------------------------------------------
// MACHINE_CONFIG_FRAGMENT( abc802_video )
//-------------------------------------------------
MACHINE_CONFIG_FRAGMENT( abc802_video )
MCFG_MC6845_ADD(MC6845_TAG, MC6845, ABC800_CCLK, crtc_intf)
MCFG_SCREEN_ADD(SCREEN_TAG, RASTER)
MCFG_SCREEN_UPDATE_DRIVER(abc802_state, screen_update)
MCFG_SCREEN_REFRESH_RATE(60)
MCFG_SCREEN_VBLANK_TIME(ATTOSECONDS_IN_USEC(2500))
MCFG_SCREEN_SIZE(768, 312)
MCFG_SCREEN_VISIBLE_AREA(0,768-1, 0, 312-1)
MACHINE_CONFIG_END
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