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AmigActive 10
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AACD 10.iso
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MAME
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machine
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galaga.c
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C/C++ Source or Header
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2000-04-23
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5KB
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261 lines
/***************************************************************************
machine.c
Functions to emulate general aspects of the machine (RAM, ROM, interrupts,
I/O ports)
***************************************************************************/
#include "driver.h"
#include "vidhrdw/generic.h"
#include "cpu/z80/z80.h"
unsigned char *galaga_sharedram;
static unsigned char interrupt_enable_1,interrupt_enable_2,interrupt_enable_3;
static void *nmi_timer;
WRITE_HANDLER( galaga_halt_w );
void galaga_vh_interrupt(void);
void galaga_init_machine(void)
{
nmi_timer = 0;
galaga_halt_w (0, 0);
}
READ_HANDLER( galaga_sharedram_r )
{
return galaga_sharedram[offset];
}
WRITE_HANDLER( galaga_sharedram_w )
{
if (offset < 0x800) /* write to video RAM */
dirtybuffer[offset & 0x3ff] = 1;
galaga_sharedram[offset] = data;
}
READ_HANDLER( galaga_dsw_r )
{
int bit0,bit1;
bit0 = (input_port_0_r(0) >> offset) & 1;
bit1 = (input_port_1_r(0) >> offset) & 1;
return bit0 | (bit1 << 1);
}
/***************************************************************************
Emulate the custom IO chip.
***************************************************************************/
static int customio_command;
static int mode,credits;
static int coinpercred,credpercoin;
static unsigned char customio[16];
WRITE_HANDLER( galaga_customio_data_w )
{
customio[offset] = data;
logerror("%04x: custom IO offset %02x data %02x\n",cpu_get_pc(),offset,data);
switch (customio_command)
{
case 0xa8:
if (offset == 3 && data == 0x20) /* total hack */
sample_start(0,0,0);
break;
case 0xe1:
if (offset == 7)
{
coinpercred = customio[1];
credpercoin = customio[2];
}
break;
}
}
READ_HANDLER( galaga_customio_data_r )
{
if (customio_command != 0x71)
logerror("%04x: custom IO read offset %02x\n",cpu_get_pc(),offset);
switch (customio_command)
{
case 0x71: /* read input */
case 0xb1: /* only issued after 0xe1 (go into credit mode) */
if (offset == 0)
{
if (mode) /* switch mode */
{
/* bit 7 is the service switch */
return readinputport(4);
}
else /* credits mode: return number of credits in BCD format */
{
int in;
static int coininserted;
in = readinputport(4);
/* check if the user inserted a coin */
if (coinpercred > 0)
{
if ((in & 0x70) != 0x70 && credits < 99)
{
coininserted++;
if (coininserted >= coinpercred)
{
credits += credpercoin;
coininserted = 0;
}
}
}
else credits = 2;
/* check for 1 player start button */
if ((in & 0x04) == 0)
if (credits >= 1) credits--;
/* check for 2 players start button */
if ((in & 0x08) == 0)
if (credits >= 2) credits -= 2;
return (credits / 10) * 16 + credits % 10;
}
}
else if (offset == 1)
return readinputport(2); /* player 1 input */
else if (offset == 2)
return readinputport(3); /* player 2 input */
break;
}
return -1;
}
READ_HANDLER( galaga_customio_r )
{
return customio_command;
}
void galaga_nmi_generate (int param)
{
cpu_cause_interrupt (0, Z80_NMI_INT);
}
WRITE_HANDLER( galaga_customio_w )
{
if (data != 0x10 && data != 0x71)
logerror("%04x: custom IO command %02x\n",cpu_get_pc(),data);
customio_command = data;
switch (data)
{
case 0x10:
if (nmi_timer) timer_remove (nmi_timer);
nmi_timer = 0;
return;
case 0xa1: /* go into switch mode */
mode = 1;
break;
case 0xe1: /* go into credit mode */
credits = 0; /* this is a good time to reset the credits counter */
mode = 0;
break;
}
nmi_timer = timer_pulse (TIME_IN_USEC (50), 0, galaga_nmi_generate);
}
WRITE_HANDLER( galaga_halt_w )
{
if (data & 1)
{
cpu_set_reset_line(1,CLEAR_LINE);
cpu_set_reset_line(2,CLEAR_LINE);
}
else if (!data)
{
cpu_set_reset_line(1,ASSERT_LINE);
cpu_set_reset_line(2,ASSERT_LINE);
}
}
WRITE_HANDLER( galaga_interrupt_enable_1_w )
{
interrupt_enable_1 = data & 1;
}
int galaga_interrupt_1(void)
{
galaga_vh_interrupt(); /* update the background stars position */
if (interrupt_enable_1) return interrupt();
else return ignore_interrupt();
}
WRITE_HANDLER( galaga_interrupt_enable_2_w )
{
interrupt_enable_2 = data & 1;
}
int galaga_interrupt_2(void)
{
if (interrupt_enable_2) return interrupt();
else return ignore_interrupt();
}
WRITE_HANDLER( galaga_interrupt_enable_3_w )
{
interrupt_enable_3 = !(data & 1);
}
int galaga_interrupt_3(void)
{
if (interrupt_enable_3) return nmi_interrupt();
else return ignore_interrupt();
}