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Add some code from MESS to emulate the Genesis gamepads #174

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Oct 28, 2024
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Add some code from MESS to emulate the Genesis gamepads #174

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234 changes: 234 additions & 0 deletions src/drivers/genesis.c
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Original file line number Diff line number Diff line change
Expand Up @@ -631,6 +631,240 @@ WRITE16_HANDLER ( genesis_io_w )

}

/* Ripped From MESS Aladdin And Bare Knuckle III Genesis Gamepad Emulation */
int genesis_region;

void genesis_init_io (void)
{

genesis_io_ram[0x00] = (genesis_region & 0xc0)| (0x00 & 0x3f); // region / pal / segacd etc. important!
genesis_io_ram[0x01] = 0x7f;
genesis_io_ram[0x02] = 0x7f;
genesis_io_ram[0x03] = 0x7f;
genesis_io_ram[0x04] = 0x00;
genesis_io_ram[0x05] = 0x00;
genesis_io_ram[0x06] = 0x00;
genesis_io_ram[0x07] = 0xff;
genesis_io_ram[0x08] = 0x00;
genesis_io_ram[0x09] = 0x00;
genesis_io_ram[0x0a] = 0xff;
genesis_io_ram[0x0b] = 0x00;
genesis_io_ram[0x0c] = 0x00;
genesis_io_ram[0x0d] = 0xfb;
genesis_io_ram[0x0e] = 0x00;
genesis_io_ram[0x0f] = 0x00;


/*
$A10001 = $80 (Bits 7,6,5 depend on the domestic/export, PAL/NTSC jumpers and having a Sega CD or not)
$A10003 = $7F
$A10005 = $7F
$A10007 = $7F
$A10009 = $00
$A1000B = $00
$A1000D = $00
$A1000F = $FF
$A10011 = $00
$A10013 = $00
$A10015 = $FF
$A10017 = $00
$A10019 = $00
$A1001B = $FB
$A1001D = $00
$A1001F = $00
*/

}

READ16_HANDLER ( genesis_68000_io_r )
{
int paddata,p;
int inlines, outlines;

//printf("I/O read .. offset %02x data %02x\n",offset,genesis_io_ram[offset]);

switch (offset)
{
case 0x00: // version register
return genesis_io_ram[offset];
case 0x01:
// printf("I/O Data A read \n");

/*
When TH=0 When TH=1
D6 : (TH) 0 1
D5 : (TR) Start button Button C
D4 : (TL) Button A Button B
D3 : (D3) 0 D-pad Right
D2 : (D2) 0 D-pad Left
D1 : (D1) D-pad Down D-pad Down
D0 : (D0) D-pad Up D-pad Up
*/

/* process pad input for std 3 button pad */


p = readinputport(0);
if (genesis_io_ram[offset]&0x40)
{
paddata = ((p&0x0f)>>0) | ((p&0xc0)>>2) | 0x40;
}
else
{
paddata = ((p&0x03)>>0) | ((p&0x30)>>0) | 0x00;
}

inlines = (genesis_io_ram[0x04]^0xff)&0x7f;
outlines = (genesis_io_ram[0x04] | 0x80);

// printf ("ioram %02x inlines %02x paddata %02x outlines %02x othdata %02x\n",genesis_io_ram[0x04], inlines, paddata, outlines, genesis_io_ram[0x01]);



p = (paddata & inlines) | (genesis_io_ram[0x01] & outlines);

return p | p << 8;


return genesis_io_ram[offset];
case 0x02:
// printf("I/O Data B read \n");

p = readinputport(1);
if (genesis_io_ram[offset]&0x40)
{
paddata = ((p&0x0f)>>0) | ((p&0xc0)>>2) | 0x40;
}
else
{
paddata = ((p&0x03)>>0) | ((p&0x30)>>0) | 0x00;
}

inlines = (genesis_io_ram[0x05]^0xff)&0x7f;
outlines = (genesis_io_ram[0x05] | 0x80);


p = (paddata & inlines) | (genesis_io_ram[0x02] & outlines);

return p | p <<8;

case 0x03:
// printf("I/O Data C read \n");
return genesis_io_ram[offset];

case 0x04:
case 0x05:
case 0x06:
case 0x07:
case 0x08:
case 0x09:
case 0x0a:
case 0x0b:
case 0x0c:
case 0x0d:
case 0x0e:
case 0x0f:
default:
printf("Unhandled I/O read \n");
return genesis_io_ram[offset];

}

return genesis_io_ram[offset];

/*
D7 : Console is 1= Export (USA, Europe, etc.) 0= Domestic (Japan)
D6 : Video type is 1= PAL, 0= NTSC
D5 : Sega CD unit is 1= not present, 0= connected.
D4 : Unused (always returns zero)
D3 : Bit 3 of version number
D2 : Bit 2 of version number
D1 : Bit 1 of version number
D0 : Bit 0 of version number
*/


// return 0x30;
// return mame_rand();
// return 0xff;
}

/*
The I/O chip is mapped to $A10000-$A1001F in the 68000/VDP/Z80 banked address space.
It is normally read and written in byte units at odd addresses. The chip gets /LWR only,
so writing to even addresses has no effect. Reading even addresses returns the same data
ou'd get from an odd address. If a word-sized write is done, the LSB is sent to the I/O chip
and the MSB is ignored.
*/

/*
$A10001 Version
$A10003 Port A data
$A10005 Port B data
$A10007 Port C data
$A10009 Port A control
$A1000B Port B control
$A1000D Port C control
$A1000F Port A TxData
$A10011 Port A RxData
$A10013 Port A serial control
$A10015 Port B TxData
$A10017 Port B RxData
$A10019 Port B serial control
$A1001B Port C TxData
$A1001D Port C RxData
$A1001F Port C serial contro
*/

WRITE16_HANDLER ( genesis_68000_io_w )
{

// printf("I/O write offset %02x data %04x\n",offset,data);

switch (offset)
{
case 0x00: // Version (read only?)
printf("attempted write to version register?!\n");
break;
case 0x01: // Port A data
// printf("write to data port A with control register A %02x step1 %02x step2 %02x\n", genesis_io_ram[0x04], (genesis_io_ram[0x01] & !((genesis_io_ram[0x04]&0x7f)|0x80)), (data & ((genesis_io_ram[0x04]&0x7f)|0x80)) );
genesis_io_ram[0x01] = (genesis_io_ram[0x01] & ((genesis_io_ram[0x04]^0xff)|0x80)) | (data & ((genesis_io_ram[0x04]&0x7f)|0x80));
break;
case 0x02: // Port B data
// printf("write to data port B with control register B %02x\n", genesis_io_ram[0x05]);
genesis_io_ram[0x02] = (genesis_io_ram[0x02] & ((genesis_io_ram[0x05]^0xff)|0x80)) | (data & ((genesis_io_ram[0x05]&0x7f)|0x80));
break;
case 0x03: // Port C data
// printf("write to data port C with control register C %02x\n", genesis_io_ram[0x06]);
genesis_io_ram[0x03] = (genesis_io_ram[0x03] & ((genesis_io_ram[0x06]^0xff)|0x80)) | (data & ((genesis_io_ram[0x06]&0x7f)|0x80));
break;
case 0x04: // Port A control
genesis_io_ram[offset]=data;
break;
case 0x05: // Port B control
genesis_io_ram[offset]=data;
break;
case 0x06: // Port C control
genesis_io_ram[offset]=data;
break;

/* unhandled */
case 0x07:
case 0x08:
case 0x09:
case 0x0a:
case 0x0b:
case 0x0c:
case 0x0d:
case 0x0e:
case 0x0f:
default:
genesis_io_ram[offset]=data;
printf("unhandled IO write (offset %02x data %02x)\n",offset,data);
break;
}
}

static ADDRESS_MAP_START( genesis_readmem, ADDRESS_SPACE_PROGRAM, 16 )
AM_RANGE(0x000000, 0x3fffff) AM_READ(MRA16_ROM) /* Cartridge Program Rom */
AM_RANGE(0xa10000, 0xa1001f) AM_READ(genesis_io_r) /* Genesis Input */
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