Genesis-Plus-GX/source/io.c
ekeeke31 217ca8de3f
2007-08-10 20:34:06 +00:00

216 lines
5.0 KiB
C

/*
Copyright (C) 1999, 2000, 2001, 2002, 2003 Charles MacDonald
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
I/O controller chip emulation
*/
#include "shared.h"
uint8 io_reg[0x10];
uint8 region_code = REGION_USA;
uint8 pad_type = DEVICE_3BUTTON;
/*****************************************************************************
* IO Read/Write wrappers
*
*****************************************************************************/
unsigned char Player1_Read (void)
{
return gamepad_read(0);
}
unsigned char Player2_Read (void)
{
return gamepad_read(4);
}
void Player1_Write (unsigned char data)
{
gamepad_write(0, data);
}
void Player2_Write (unsigned char data)
{
gamepad_write(4, data);
}
unsigned char MultiTap1_Read (void)
{
return multitap_read(0);
}
unsigned char MultiTap2_Read (void)
{
return multitap_read(1);
}
void MultiTap1_Write (unsigned char data)
{
multitap_write(0, data);
}
void MultiTap2_Write (unsigned char data)
{
multitap_write(1, data);
}
/*****************************************************************************
* I/O chip functions *
* *
*****************************************************************************
*/
struct port_t
{
void (*data_w)(uint8 data);
uint8 (*data_r)(void);
} port[3];
void io_reset(void)
{
/* I/O register default settings */
uint8 io_def[0x10] =
{
0xA0,
0x7F, 0x7F, 0x7F,
0x00, 0x00, 0x00,
0xFF, 0x00, 0x00,
0xFF, 0x00, 0x00,
0xFB, 0x00, 0x00,
};
/* Initialize I/O registers */
memcpy (io_reg, io_def, 0x10);
switch (input.system[0])
{
case SYSTEM_GAMEPAD:
port[0].data_w = Player1_Write;
port[0].data_r = Player1_Read;
break;
case SYSTEM_WAYPLAY:
case SYSTEM_TEAMPLAYER:
port[0].data_w = MultiTap1_Write;
port[0].data_r = MultiTap1_Read;
break;
default:
port[0].data_w = NULL;
port[0].data_r = NULL;
break;
}
switch (input.system[1])
{
case SYSTEM_GAMEPAD:
port[1].data_w = Player2_Write;
port[1].data_r = Player2_Read;
break;
case SYSTEM_WAYPLAY:
case SYSTEM_TEAMPLAYER:
port[1].data_w = MultiTap2_Write;
port[1].data_r = MultiTap2_Read;
break;
case SYSTEM_MENACER:
port[1].data_w = NULL;
port[1].data_r = lightgun_read;
break;
default:
port[1].data_w = NULL;
port[1].data_r = NULL;
break;
}
port[2].data_w = NULL;
port[2].data_r = NULL;
j_cart = 0;
input_reset(pad_type);
}
void io_write(int offset, int value)
{
switch (offset)
{
case 0x01: /* Port A Data */
case 0x02: /* Port B Data */
case 0x03: /* Port C Data */
io_reg[offset] = ((value & 0x80) | (value & io_reg[offset+3]));
if(port[offset-1].data_w) port[offset-1].data_w(value);
return;
case 0x05: /* Port B Ctrl */
if (((value & 0x7F) == 0x7F) &&
((input.system[0] == SYSTEM_TEAMPLAYER) ||
(input.system[1] == SYSTEM_TEAMPLAYER)))
{
/* autodetect 4-Way play ! */
input.system[0] = SYSTEM_WAYPLAY;
input.system[1] = SYSTEM_WAYPLAY;
port[0].data_w = MultiTap1_Write;
port[0].data_r = MultiTap1_Read;
port[1].data_w = MultiTap2_Write;
port[1].data_r = MultiTap2_Read;
input_reset(pad_type);
}
case 0x04: /* Port A Ctrl */
case 0x06: /* Port C Ctrl */
io_reg[offset] = value & 0xFF;
io_reg[offset-3] = ((io_reg[offset-3] & 0x80) | (io_reg[offset-3] & io_reg[offset]));
break;
case 0x07: /* Port A TxData */
case 0x0A: /* Port B TxData */
case 0x0D: /* Port C TxData */
io_reg[offset] = value;
break;
case 0x09: /* Port A S-Ctrl */
case 0x0C: /* Port B S-Ctrl */
case 0x0F: /* Port C S-Ctrl */
io_reg[offset] = (value & 0xF8);
break;
}
}
int io_read(int offset)
{
uint8 has_scd = 0x20; /* No Sega CD unit attached */
uint8 gen_ver = 0x00; /* Version 0 hardware */
uint8 input = 0x7F; /* default input state */
switch(offset)
{
case 0x00: /* Version */
return (region_code | has_scd | gen_ver);
case 0x01: /* Port A Data */
case 0x02: /* Port B Data */
case 0x03: /* Port C Data */
if(port[offset-1].data_r) input = port[offset-1].data_r();
return (io_reg[offset] | ((~io_reg[offset+3]) & input));
}
return (io_reg[offset]);
}