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berzerk.c
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C/C++ Source or Header
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2000-04-04
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125 lines
/***************************************************************************
machine.c
Functions to emulate general aspects of the machine (RAM, ROM, interrupts,
I/O ports)
***************************************************************************/
#include "driver.h"
#include "cpu/z80/z80.h"
static int irq_enabled;
static int nmi_enabled;
int berzerk_irq_end_of_screen;
int berzerkplayvoice;
static int int_count;
void berzerk_init_machine(void)
{
int i;
/* Berzerk expects locations 3800-3fff to be ff */
for (i = 0x3800; i < 0x4000; i++)
memory_region(REGION_CPU1)[i] = 0xff;
irq_enabled = 0;
nmi_enabled = 0;
berzerk_irq_end_of_screen = 0;
int_count = 0;
}
WRITE_HANDLER( berzerk_irq_enable_w )
{
irq_enabled = data;
}
WRITE_HANDLER( berzerk_nmi_enable_w )
{
nmi_enabled = 1;
}
WRITE_HANDLER( berzerk_nmi_disable_w )
{
nmi_enabled = 0;
}
READ_HANDLER( berzerk_nmi_enable_r )
{
nmi_enabled = 1;
return 0;
}
READ_HANDLER( berzerk_nmi_disable_r )
{
nmi_enabled = 0;
return 0;
}
READ_HANDLER( berzerk_led_on_r )
{
osd_led_w(0,1);
return 0;
}
READ_HANDLER( berzerk_led_off_r )
{
osd_led_w(0,0);
return 0;
}
READ_HANDLER( berzerk_voiceboard_r )
{
if (!berzerkplayvoice)
return 0;
else
return 0x40;
}
int berzerk_interrupt(void)
{
int_count++;
switch (int_count)
{
default:
case 4:
case 8:
if (int_count == 8)
{
berzerk_irq_end_of_screen = 0;
int_count = 0;
}
else
{
berzerk_irq_end_of_screen = 1;
}
return irq_enabled ? 0xfc : Z80_IGNORE_INT;
case 1:
case 2:
case 3:
case 5:
case 6:
case 7:
if (int_count == 7)
{
berzerk_irq_end_of_screen = 1;
}
else
{
berzerk_irq_end_of_screen = 0;
}
return nmi_enabled ? Z80_NMI_INT : Z80_IGNORE_INT;
}
}