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// license:BSD-3-Clause
// copyright-holders:Miodrag Milanovic, Jonathan Gevaryahu
/***************************************************************************

        DEC VT520

        02/07/2009 Skeleton driver.

****************************************************************************/

#include "emu.h"
#include "machine/ram.h"
#include "cpu/mcs51/mcs51.h"


class vt520_state : public driver_device
{
public:
	vt520_state(const machine_config &mconfig, device_type type, const char *tag)
		: driver_device(mconfig, type, tag) ,
		m_maincpu(*this, "maincpu") { }

	DECLARE_READ8_MEMBER(vt520_some_r);
	virtual void machine_reset();
	virtual void video_start();
	UINT32 screen_update_vt520(screen_device &screen, bitmap_ind16 &bitmap, const rectangle &cliprect);
	required_device<cpu_device> m_maincpu;
};


static ADDRESS_MAP_START(vt520_mem, AS_PROGRAM, 8, vt520_state)
	AM_RANGE(0x0000, 0xffff) AM_RAMBANK("bank1")
ADDRESS_MAP_END

/*
    On the board there is TC160G41AF (1222) custom chip
    doing probably all video/uart logic
    there is 43.430MHz xtal near by
*/

READ8_MEMBER( vt520_state::vt520_some_r )
{
	//bit 5 0
	//bit 6 1
	return 0x40;
}

static ADDRESS_MAP_START(vt520_io, AS_IO, 8, vt520_state)
	ADDRESS_MAP_UNMAP_HIGH
	AM_RANGE(0x7ffb, 0x7ffb) AM_READ(vt520_some_r)
ADDRESS_MAP_END

/* Input ports */
static INPUT_PORTS_START( vt520 )
INPUT_PORTS_END


void vt520_state::machine_reset()
{
	address_space &space = m_maincpu->space(AS_PROGRAM);
	UINT8 *rom = memregion("maincpu")->base();
	space.unmap_write(0x0000, 0xffff);
	membank("bank1")->set_base(rom + 0x70000);
}

void vt520_state::video_start()
{
}

UINT32 vt520_state::screen_update_vt520(screen_device &screen, bitmap_ind16 &bitmap, const rectangle &cliprect)
{
	return 0;
}

static MACHINE_CONFIG_START( vt520, vt520_state )
	/* basic machine hardware */
	MCFG_CPU_ADD("maincpu",I8032, XTAL_20MHz)
	MCFG_CPU_PROGRAM_MAP(vt520_mem)
	MCFG_CPU_IO_MAP(vt520_io)


	/* video hardware */
	MCFG_SCREEN_ADD("screen", RASTER)
	MCFG_SCREEN_REFRESH_RATE(50)
	MCFG_SCREEN_VBLANK_TIME(ATTOSECONDS_IN_USEC(2500)) /* not accurate */
	MCFG_SCREEN_SIZE(802, 480)
	MCFG_SCREEN_VISIBLE_AREA(0, 802-1, 0, 480-1)
	MCFG_SCREEN_UPDATE_DRIVER(vt520_state, screen_update_vt520)
	MCFG_SCREEN_PALETTE("palette")

	MCFG_PALETTE_ADD_BLACK_AND_WHITE("palette")

	// On the board there are two M5M44256BJ-7 chips
	// Which are DRAM 256K x 4bit
	/* internal ram */
	MCFG_RAM_ADD(RAM_TAG)
	MCFG_RAM_DEFAULT_SIZE("256K")
MACHINE_CONFIG_END

/* ROM definition */
ROM_START( vt520 )
	ROM_REGION( 0x80000, "maincpu", ROMREGION_ERASEFF )
	ROM_LOAD( "23-010ed-00.e20", 0x0000, 0x80000, CRC(2502cc22) SHA1(0437c3107412f69e09d050fef003f2a81d8a3163)) // "(C)DEC94 23-010ED-00 // 9739 D" dumped from a VT520-A4 model
ROM_END

/* Driver */

/*    YEAR  NAME    PARENT  COMPAT   MACHINE   INPUT    INIT     COMPANY                     FULLNAME       FLAGS */
//COMP( 1993, vt510,  0,      0,       vt520,    vt520, driver_device,   0,  "Digital Equipment Corporation", "VT510", MACHINE_NOT_WORKING)
COMP( 1994, vt520,  0,      0,       vt520,    vt520, driver_device,   0,  "Digital Equipment Corporation", "VT520", MACHINE_NOT_WORKING | MACHINE_NO_SOUND)
//COMP( 1994, vt525,  0,      0,       vt520,    vt520, driver_device,   0,  "Digital Equipment Corporation", "VT525", MACHINE_NOT_WORKING)