/***************************************************************************
machine.c
Functions to emulate general aspects of the machine (RAM, ROM, interrupts,
I/O ports)
***************************************************************************/
#include "driver.h"
#include "cpu/z80/z80.h"
#include "sound/msm5205.h"
// this prototype will move to the driver
static WRITE8_HANDLER( stfight_bank_w );
/*
Encryption PAL 16R4 on CPU board
+---U---+
CP --| |-- VCC
ROM D1 --| |-- ROM D0 M1 = 0 M1 = 1
ROM D3 --| |-- (NC)
ROM D4 --| |-- D6 D6 = D1 ^^ D3 D6 = / ( D1 ^^ D0 )
ROM D6 --| |-- D4 D4 = / ( D6 ^^ A7 ) D4 = D3 ^^ A0
A0 --| |-- D3 D3 = / ( D0 ^^ A1 ) D3 = D4 ^^ A4
A1 --| |-- D0 D0 = D1 ^^ D4 D0 = / ( D6 ^^ A0 )
A4 --| |-- (NC)
A7 --| |-- /M1
GND --| |-- /OE
+-------+
*/
static UINT8 *decrypt;
DRIVER_INIT( empcity )
{
UINT8 *rom = memory_region(REGION_CPU1);
int A;
decrypt = auto_malloc(0x8000);
memory_set_decrypted_region(0, 0x0000, 0x7fff, decrypt);
for (A = 0;A < 0x8000;A++)
{
UINT8 src = rom[A];
// decode opcode
decrypt[A] =
( src & 0xA6 ) |
( ( ( ( src << 2 ) ^ src ) << 3 ) & 0x40 ) |
( ~( ( src ^ ( A >> 1 ) ) >> 2 ) & 0x10 ) |
( ~( ( ( src << 1 ) ^ A ) << 2 ) & 0x08 ) |
( ( ( src ^ ( src >> 3 ) ) >> 1 ) & 0x01 );
// decode operand
rom[A] =
( src & 0xA6 ) |
( ~( ( src ^ ( src << 1 ) ) << 5 ) & 0x40 ) |
( ( ( src ^ ( A << 3 ) ) << 1 ) & 0x10 ) |
( ( ( src ^ A ) >> 1 ) & 0x08 ) |
( ~( ( src >> 6 ) ^ A ) & 0x01 );
}
}
DRIVER_INIT( stfight )
{
driver_init_empcity(machine);
/* patch out a tight loop during startup - is the code waiting */
/* for NMI to wake it up? */
decrypt[0xb1] = 0x00;
decrypt[0xb2] = 0x00;
decrypt[0xb3] = 0x00;
decrypt[0xb4] = 0x00;
decrypt[0xb5] = 0x00;
}
MACHINE_RESET( stfight )
{
// initialise rom bank
stfight_bank_w( 0, 0 );
}
// It's entirely possible that this bank is never switched out
// - in fact I don't even know how/where it's switched in!
static WRITE8_HANDLER( stfight_bank_w )
{
UINT8 *ROM2 = memory_region(REGION_CPU1) + 0x10000;
memory_set_bankptr( 1, &ROM2[data<<14] );
}
/*
* CPU 1 timed interrupt - 60Hz???
*/
static TIMER_CALLBACK( stfight_interrupt_1 )
{
// Do a RST08
cpunum_set_input_line_and_vector(0,0,HOLD_LINE,0xcf);
}
INTERRUPT_GEN( stfight_vb_interrupt )
{
// Do a RST10
cpunum_set_input_line_and_vector(0,0,HOLD_LINE,0xd7);
timer_set(ATTOTIME_IN_HZ(120), 0, stfight_interrupt_1);
}
/*
* Hardware handlers
*/
// Perhaps define dipswitches as active low?
READ8_HANDLER( stfight_dsw_r )
{
return( ~readinputport( 3+offset ) );
}
static int stfight_coin_mech_query_active = 0;
static int stfight_coin_mech_query;
READ8_HANDLER( stfight_coin_r )
{
static int coin_mech_latch[2] = { 0x02, 0x01 };
int coin_mech_data;
int i;
// Was the coin mech queried by software?
if( stfight_coin_mech_query_active )
{
stfight_coin_mech_query_active = 0;
return( (~stfight_coin_mech_query) & 0x03 );
}
/*
* Is this really necessary?
* - we can control impulse length so that the port is
* never strobed twice within the impulse period
* since it's read by the 30Hz interrupt ISR
*/
coin_mech_data = readinputport( 5 );
for( i=0; i<2; i++ )
{
/* Only valid on signal edge */
if( ( coin_mech_data & (1<<i) ) != coin_mech_latch[i] )
coin_mech_latch[i] = coin_mech_data & (1<<i);
else
coin_mech_data |= coin_mech_data & (1<<i);
}
return( coin_mech_data );
}
WRITE8_HANDLER( stfight_coin_w )
{
// interrogate coin mech
stfight_coin_mech_query_active = 1;
stfight_coin_mech_query = data;
}
/*
* Machine hardware for MSM5205 ADPCM sound control
*/
static int sampleLimits[] =
{
0x0000, // machine gun fire?
0x1000, // player getting shot
0x2C00, // player shooting
0x3C00, // girl screaming
0x5400, // girl getting shot
0x7200 // (end of samples)
};
static int adpcm_data_offs;
static int adpcm_data_end;
void stfight_adpcm_int( int data )
{
static int toggle;
UINT8 *SAMPLES = memory_region(REGION_SOUND1);
int adpcm_data = SAMPLES[adpcm_data_offs & 0x7fff];
// finished playing sample?
if( adpcm_data_offs == adpcm_data_end )
{
MSM5205_reset_w( 0, 1 );
return;
}
if( toggle == 0 )
MSM5205_data_w( 0, ( adpcm_data >> 4 ) & 0x0f );
else
{
MSM5205_data_w( 0, adpcm_data & 0x0f );
adpcm_data_offs++;
}
toggle ^= 1;
}
WRITE8_HANDLER( stfight_adpcm_control_w )
{
if( data < 0x08 )
{
adpcm_data_offs = sampleLimits[data];
adpcm_data_end = sampleLimits[data+1];
}
MSM5205_reset_w( 0, data & 0x08 ? 1 : 0 );
}
WRITE8_HANDLER( stfight_e800_w )
{
}
/*
* Machine hardware for YM2303 fm sound control
*/
static UINT8 fm_data;
WRITE8_HANDLER( stfight_fm_w )
{
// the sound cpu ignores any fm data without bit 7 set
fm_data = 0x80 | data;
}
READ8_HANDLER( stfight_fm_r )
{
int data = fm_data;
// clear the latch?!?
fm_data &= 0x7f;
return( data );
}