// license:BSD-3-Clause
// copyright-holders:David Haywood, Mariusz Wojcieszek
/*
tiny bartop b&w Space Invaders type game with colour overlay
Driver by David Haywood and Mariusz Wojcieszek
TODO:
- 16 bytes are protected in the c*** range. I'm guessing they used a PROM to protect a
simple sub-routine because:
* It attempts to jsr from RAM to that area with a 0x10 byte offset (i.e. ROM copies a code snippet to RAM; when it executes
it code executes jsr 0xc400 then self-modifies it to 0xc410, rinse and repeat ... up to 0xc7f0 and rolls back);
* After that the program has an amusing left-over located at 0xe000-0xe00f (yup, NOPs + a RTS), with the
exact same number of times as above;
It's unknown at current stage what it really protects tho, game seems working for all I can see ... -AS
- Sound is entirely guesswork.
*/
#include "emu.h"
#include "cpu/m6502/m6502.h"
#include "sound/discrete.h"
#include "screen.h"
#include "speaker.h"
#include "alinvade.lh"
class alinvade_state : public driver_device
{
public:
alinvade_state(const machine_config &mconfig, device_type type, const char *tag)
: driver_device(mconfig, type, tag)
, m_maincpu(*this, "maincpu")
, m_videoram(*this, "videoram")
, m_discrete(*this, "discrete")
{ }
void alinvade(machine_config &config);
private:
DECLARE_READ8_MEMBER(irqmask_r);
DECLARE_WRITE8_MEMBER(irqmask_w);
DECLARE_WRITE8_MEMBER(sound_w);
DECLARE_WRITE8_MEMBER(sounden_w);
DECLARE_WRITE_LINE_MEMBER(vblank_irq);
uint32_t screen_update(screen_device &screen, bitmap_rgb32 &bitmap, const rectangle &cliprect);
void alinvade_map(address_map &map);
uint8_t m_irqmask;
uint8_t m_irqff;
virtual void machine_start() override;
virtual void machine_reset() override;
required_device<cpu_device> m_maincpu;
required_shared_ptr<uint8_t> m_videoram;
required_device<discrete_device> m_discrete;
};
static const discrete_dac_r1_ladder alinvade_music_dac =
{3, {0, RES_K(47), RES_K(12)}, 0, 0, 0, CAP_U(0.01)};
#define ALINVADE_MUSIC_CLK (75000)
DISCRETE_SOUND_START(alinvade_discrete)
DISCRETE_INPUT_DATA (NODE_01)
DISCRETE_NOTE(NODE_20, 1, ALINVADE_MUSIC_CLK, NODE_01, 255, 5, DISC_CLK_IS_FREQ)
// Convert count to 7492 output
DISCRETE_TRANSFORM2(NODE_21, NODE_20, 2, "01>0+")
DISCRETE_DAC_R1(NODE_22, NODE_21, DEFAULT_TTL_V_LOGIC_1, &alinvade_music_dac)
DISCRETE_CRFILTER(NODE_80, NODE_22, RES_K(10), CAP_U(0.1))
DISCRETE_OUTPUT(NODE_80, 2500)
DISCRETE_SOUND_END
WRITE8_MEMBER( alinvade_state::sound_w )
{
m_discrete->write(NODE_01, (data^0x3f)<<2);
}
WRITE8_MEMBER( alinvade_state::sounden_w )
{
machine().sound().system_enable(data == 4);
}
READ8_MEMBER(alinvade_state::irqmask_r)
{
return 0; // TODO: might be anything
}
WRITE8_MEMBER(alinvade_state::irqmask_w)
{
if((!(m_irqff & 1)) && (data & 1)) // f/f, active high? If the above actually returns 0xff this could be active low ...
m_irqmask^= 1;
m_irqff = data;
}
void alinvade_state::alinvade_map(address_map &map)
{
map(0x0000, 0x01ff).ram();
map(0x0400, 0x0bff).ram().share("videoram");
map(0x0c00, 0x0dff).ram();
map(0x2000, 0x2000).w(FUNC(alinvade_state::sound_w));
map(0x4000, 0x4000).portr("COIN");
map(0x6000, 0x6000).portr("DSW");
map(0x8000, 0x8000).portr("IN0");
map(0x8001, 0x8001).portr("IN1");
map(0x8002, 0x8002).portr("IN2");
map(0x8003, 0x8003).portr("IN3");
map(0x8004, 0x8004).portr("IN4");
map(0xa000, 0xa000).nopw(); //??
map(0xc000, 0xc00f).mirror(0xff0).rom().region("proms", 0);
map(0xe000, 0xe3ff).rom();
map(0xe400, 0xe400).w(FUNC(alinvade_state::sounden_w));
map(0xe800, 0xe800).rw(FUNC(alinvade_state::irqmask_r), FUNC(alinvade_state::irqmask_w)); //??
map(0xec00, 0xffff).rom();
}
static INPUT_PORTS_START( alinvade )
PORT_START("COIN")
PORT_BIT(0x10, IP_ACTIVE_LOW, IPT_COIN1 )
PORT_BIT(0xef, IP_ACTIVE_LOW, IPT_UNKNOWN )
PORT_START("IN0")
PORT_BIT(0x20, IP_ACTIVE_HIGH, IPT_BUTTON1 ) PORT_PLAYER(1)
PORT_BIT(0xdf, IP_ACTIVE_HIGH, IPT_UNKNOWN )
PORT_START("IN1")
PORT_BIT(0x20, IP_ACTIVE_HIGH, IPT_JOYSTICK_RIGHT ) PORT_2WAY PORT_PLAYER(1)
PORT_BIT(0xdf, IP_ACTIVE_HIGH, IPT_UNKNOWN )
PORT_START("IN2")
PORT_BIT(0x20, IP_ACTIVE_HIGH, IPT_JOYSTICK_LEFT ) PORT_2WAY PORT_PLAYER(1)
PORT_BIT(0xdf, IP_ACTIVE_HIGH, IPT_UNKNOWN )
PORT_START("IN3")
PORT_BIT(0x20, IP_ACTIVE_HIGH, IPT_START1 )
PORT_BIT(0xdf, IP_ACTIVE_HIGH, IPT_UNKNOWN )
PORT_START("IN4")
PORT_BIT(0x20, IP_ACTIVE_HIGH, IPT_START2 )
PORT_BIT(0xdf, IP_ACTIVE_HIGH, IPT_UNKNOWN )
PORT_START("DSW")
PORT_DIPNAME( 0x03, 0x00, DEF_STR( Lives ) )
PORT_DIPSETTING( 0x00, "2" )
PORT_DIPSETTING( 0x01, "3" )
PORT_DIPSETTING( 0x02, "4" )
PORT_DIPSETTING( 0x03, "5" )
PORT_DIPNAME( 0x04, 0x00, DEF_STR ( Unknown ) ) // read, but not tested afterwards?
PORT_DIPSETTING( 0x00, DEF_STR( Off ) )
PORT_DIPSETTING( 0x04, DEF_STR( On ) )
PORT_BIT( 0xf8, IP_ACTIVE_HIGH, IPT_UNUSED )
INPUT_PORTS_END
void alinvade_state::machine_start()
{
save_item(NAME(m_irqff));
save_item(NAME(m_irqmask));
}
void alinvade_state::machine_reset()
{
m_irqmask = 1;
}
uint32_t alinvade_state::screen_update(screen_device &screen, bitmap_rgb32 &bitmap, const rectangle &cliprect)
{
offs_t offs;
for (offs = 0; offs < m_videoram.bytes(); offs++)
{
int i;
uint8_t x = (offs << 3)&0x7f;
int y = (offs >> 4)&0x7f;
uint8_t data = m_videoram[offs];
for (i = 0; i < 8; i++)
{
pen_t pen = (data & 0x01) ? rgb_t::white() : rgb_t::black();
bitmap.pix32(y, x) = pen;
data = data >> 1;
x = x + 1;
}
}
return 0;
}
WRITE_LINE_MEMBER(alinvade_state::vblank_irq)
{
if (state && BIT(m_irqmask, 0))
m_maincpu->set_input_line(0,HOLD_LINE);
}
MACHINE_CONFIG_START(alinvade_state::alinvade)
/* basic machine hardware */
MCFG_DEVICE_ADD("maincpu", M6502,2000000) /* ? MHz */
MCFG_DEVICE_PROGRAM_MAP(alinvade_map)
/* video hardware */
MCFG_SCREEN_ADD("screen", RASTER)
MCFG_SCREEN_REFRESH_RATE(60)
MCFG_SCREEN_VBLANK_TIME(ATTOSECONDS_IN_USEC(0))
MCFG_SCREEN_SIZE(128, 128)
MCFG_SCREEN_VISIBLE_AREA(0, 128-1, 0, 128-1)
MCFG_SCREEN_UPDATE_DRIVER(alinvade_state, screen_update)
MCFG_SCREEN_VBLANK_CALLBACK(WRITELINE(*this, alinvade_state, vblank_irq))
/* sound hardware */
SPEAKER(config, "mono").front_center();
MCFG_DEVICE_ADD("discrete", DISCRETE, alinvade_discrete)
MCFG_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.0)
MACHINE_CONFIG_END
ROM_START( alinvade )
ROM_REGION( 0x10000, "maincpu", 0 ) // todo, check mapping
ROM_LOAD( "alien28.708", 0xe000, 0x0400, CRC(de376295) SHA1(e8eddbb1be1f8661c6b5b39c0d78a65bded65db2) )
ROM_LOAD( "alien29.708", 0xec00, 0x0400, CRC(20212977) SHA1(9d24a6b403d968267079fa6241545bd5a01afebb) )
ROM_LOAD( "alien30.708", 0xf000, 0x0400, CRC(734b691c) SHA1(9e562159061eecf4b1dee4ea0ee4752c901a54aa) )
ROM_LOAD( "alien31.708", 0xf400, 0x0400, CRC(5a70535c) SHA1(2827e7d4bffca78bd035da04481e1e972ee2da39) )
ROM_LOAD( "alien32.708", 0xf800, 0x0400, CRC(332dd234) SHA1(9974668344a2a351868a9e7757d1c3a497dc5621) )
ROM_LOAD( "alien33.708", 0xfc00, 0x0400, CRC(e0d57fc7) SHA1(7b8ddcb4a86811592d2d0bbc61b2f19e5caa9ccc) )
ROM_REGION( 0x20, "proms", 0 )
ROM_LOAD( "prom", 0, 0x20, NO_DUMP )
ROM_FILL( 0x00, 0x0f, 0xea )
ROM_FILL( 0x0f, 0x01, 0x60 ) // rts for whole area, interrupt code jumps to various addresses here, check note on top.
ROM_END
GAMEL( 198?, alinvade, 0, alinvade, alinvade, alinvade_state, empty_init, ROT90, "Forbes?", "Alien Invaders", MACHINE_UNEMULATED_PROTECTION | MACHINE_IMPERFECT_SOUND | MACHINE_SUPPORTS_SAVE, layout_alinvade )