/***************************************************************************

The following Namco custom chips are all instances of the same 4-bit MCU,
the Fujitsu MB8843 (42-pin DIP package) and MB8842/MB8844 (28-pin DIP),
differently programmed.

chip  MCU   pins function
---- ------ ---- --------
50XX MB8842  28  player score handling (protection)
51XX MB8843  42  I/O (coin management built-in)
52XX MB8843  42  sample playback
53XX MB8843  42  I/O (steering wheel support)
54XX MB8844  28  explosion (noise) generator
56XX         42  I/O (coin management built-in)
58XX         42  I/O (coin management built-in)
62XX         28  I/O and explosion (noise) generator

06XX interface:
---------------
Galaga                  51XX  ----  ----  54XX
Bosconian (CPU board)   51XX  ----  50XX  54XX
Bosconian (Video board) 50XX  52XX  ----  ----
Xevious                 51XX  ----  50XX  54XX
Dig Dug                 51XX  53XX  ----  ----
Pole Position / PP II   51XX  53XX  52XX  54XX

16XX interface:
---------------
Super Pac Man           56XX  56XX  ----  ----
Pac & Pal               56XX  59XX  ----  ----
Mappy                   58XX  58XX  ----  ----
Phozon                  58XX  56XX  ----  ----
The Tower of Druaga     58XX  56XX  ----  ----
Grobda                  58XX  56XX  ----  ----
Dig Dug II              58XX  56XX  ----  ----
Motos                   56XX  56XX  ----  ----
Gaplus                  56XX  58XX  62XX  ----
Gaplus (alt.)           58XX  56XX  62XX  ----
Libble Rabble           58XX  56XX  56XX  ----
Toy Pop                 58XX  56XX  56XX  ----


Pinouts:

        MB8843                   MB8842/MB8844
       +------+                    +------+
  EXTAL|1   42|Vcc            EXTAL|1   28|Vcc
   XTAL|2   41|K3              XTAL|2   27|K3
 /RESET|3   40|K2            /RESET|3   26|K2
   /IRQ|4   39|K1                O0|4   25|K1
     SO|5   38|K0                O1|5   24|K0
     SI|6   37|R15               O2|6   23|R10 /IRQ
/SC /TO|7   36|R14               O3|7   22|R9 /TC
    /TC|8   35|R13               O4|8   21|R8
     P0|9   34|R12               O5|9   20|R7
     P1|10  33|R11               O6|10  19|R6
     P2|11  32|R10               O7|11  18|R5
     P3|12  31|R9                R0|12  17|R4
     O0|13  30|R8                R1|13  16|R3
     O1|14  29|R7               GND|14  15|R2
     O2|15  28|R6                  +------+
     O3|16  27|R5
     O4|17  26|R4
     O5|18  25|R3
     O6|19  24|R2
     O7|20  23|R1
    GND|21  22|R0
       +------+


      O  O  R  R  R  K
50XX  O  O  I     I  I
54XX  O  O  I  O     I
62XX  O  O  IO O     I

      P  O  O  R  R  R  R  K
51XX  O  O  O  I  I  I  I  I
52XX  O  O  O  I  I  O  O  I
53XX  O? O  O  I  I  I  I  I
56XX  O  O  O  I  I  I  IO I
58XX  O  O  O  I  I  I  IO I
59XX  O  O  O  I  I  I  IO I


For the 52XX, see sound/namco52.c

For the 54XX, see audio/namco54.c


Namco custom I/O chips 56XX, 58XX, 59XX

These chips work together with a 16XX, that interfaces them with the buffer
RAM. Each chip uses 16 nibbles of memory; the 16XX supports up to 4 chips,
but most games use only 2.

The 56XX, 58XX and 59XX are pin-to-pin compatible, but not functionally equivalent:
they provide the same functions, but the command codes and memory addresses
are different, so they cannot be exchanged.

The devices have 42 pins. There are 16 input lines and 8 output lines to be
used for I/O.


pin   description
---   -----------
1     clock (Mappy, Super Pac-Man)
2     clock (Gaplus; equivalent to the above?)
3     reset
4     irq
5-6   (to/from 16XX) (this is probably a normal I/O port used to synchronize with the 16XX)
7-8   ?
9-12  address to r/w from RAM; 12 also goes to the 16XX and acts as r/w line, so
      the chip can only read from addresses 0-7 and only write to addresses 8-F
      (this is probably a normal I/O port used for that purpose)
13-16 out port A
17-20 out port B
21    GND
22-25 in port B
26-29 in port C
30-33 in port D
34-37 (to 16XX) probably data to r/w from RAM
      (this is probably a normal I/O port used for that purpose)
38-41 in port A
42    Vcc

TODO:
- It's likely that the 56XX and 58XX chips, when in "coin mode", also internally
  handle outputs for start lamps, coin counters and coin lockout, like the 51XX.
  Such lines are NOT present in the Mappy and Super Pacman schematics, so they
  were probably not used for those games, but they might have been used in
  others (most likely Gaplus).

***************************************************************************/

#include "driver.h"
#include "machine/namcoio.h"
#include "machine/namco50.h"
#include "sound/namco52.h"
#include "audio/namco54.h"


#define VERBOSE 0

struct namcoio
{
	INT32 type;
	read8_handler in[4];
	write8_handler out[2];
	INT32 reset;
	INT32 lastcoins,lastbuttons;
	INT32 credits;
	INT32 coins[2];
	INT32 coins_per_cred[2];
	INT32 creds_per_coin[2];
	INT32 in_count;
	INT32 mode,coincred_mode,remap_joy;	// for 51XX
};

static struct namcoio io[MAX_NAMCOIO];
static INT32 nmi_cpu[MAX_06XX];
static mame_timer *nmi_timer[MAX_06XX];

static READ8_HANDLER( nop_r ) { return 0x0f; }
static WRITE8_HANDLER( nop_w ) { }

#define READ_PORT(n)	(io[chip].in[n](0) & 0x0f)
#define WRITE_PORT(n,d)	io[chip].out[n](0,(d) & 0x0f)



/*
51XX

commands:
00: nop
01 + 4 arguments: set coinage (xevious, possibly because of a bug, is different)
02: go in "credit" mode and enable start buttons
03: disable joystick remapping
04: enable joystick remapping
05: go in "switch" mode
06: nop
07: nop
*/

void namcoio_51XX_write(int chip,int data)
{
	data &= 0x07;

#if VERBOSE
	logerror("%04x: custom 51XX write %02x\n",activecpu_get_pc(),data);
#endif

	if (io[chip].coincred_mode)
	{
		switch (io[chip].coincred_mode--)
		{
			case 4: io[chip].coins_per_cred[0] = data; break;
			case 3: io[chip].creds_per_coin[0] = data; break;
			case 2: io[chip].coins_per_cred[1] = data; break;
			case 1: io[chip].creds_per_coin[1] = data; break;
		}
	}
	else
	{
		switch (data)
		{
			case 0:	// nop
				break;

			case 1:	// set coinage
				io[chip].coincred_mode = 4;
				/* this is a good time to reset the credits counter */
				io[chip].credits = 0;

				{
					/* kludge for a possible bug in Xevious */
					static const game_driver *namcoio_51XX_driver = NULL;
					static int namcoio_51XX_kludge = 0;

					/* Only compute namcoio_51XX_kludge when gamedrv changes */
					if (namcoio_51XX_driver != Machine->gamedrv)
					{
						namcoio_51XX_driver = Machine->gamedrv;
						if (strcmp(namcoio_51XX_driver->name, "xevious") == 0 ||
							strcmp(namcoio_51XX_driver->parent, "xevious") == 0)
							namcoio_51XX_kludge = 1;
						else
							namcoio_51XX_kludge = 0;
					}

					if (namcoio_51XX_kludge)
					{
						io[chip].coincred_mode = 6;
						io[chip].remap_joy = 1;
					}
				}
				break;

			case 2:	// go in "credits" mode and enable start buttons
				io[chip].mode = 1;
				io[chip].in_count = 0;
				break;

			case 3:	// disable joystick remapping
				io[chip].remap_joy = 0;
				break;

			case 4:	// enable joystick remapping
				io[chip].remap_joy = 1;
				break;

			case 5:	// go in "switch" mode
				io[chip].mode = 0;
				io[chip].in_count = 0;
				break;

			default:
				logerror("unknown 51XX command %02x\n",data);
				break;
		}
	}
}


/* joystick input mapping

  The joystick is parsed and a number corresponding to the direction is returned,
  according to the following table:

          0
        7   1
      6   8   2
        5   3
          4

  The values for directions impossible to obtain on a joystick have not been
  verified on Namco original hardware, but they are the same in all the bootlegs,
  so we can assume they are right.
*/
static int joy_map[16] =
/*  LDRU, LDR, LDU,  LD, LRU, LR,  LU,    L, DRU,  DR,  DU,   D,  RU,   R,   U, center */
{	 0xf, 0xe, 0xd, 0x5, 0xc, 0x9, 0x7, 0x6, 0xb, 0x3, 0xa, 0x4, 0x1, 0x2, 0x0, 0x8 };


UINT8 namcoio_51XX_read(int chip)
{
#if VERBOSE
	logerror("%04x: custom 51XX read\n",activecpu_get_pc());
#endif

	if (io[chip].mode == 0)	/* switch mode */
	{
		switch ((io[chip].in_count++) % 3)
		{
			default:
			case 0: return READ_PORT(0) | (READ_PORT(1) << 4);
			case 1: return READ_PORT(2) | (READ_PORT(3) << 4);
			case 2: return 0;	// nothing?
		}
	}
	else	/* credits mode */
	{
		switch ((io[chip].in_count++) % 3)
		{
			default:
			case 0:	// number of credits in BCD format
				{
					int in,toggle;

					in = ~(READ_PORT(0) | (READ_PORT(1) << 4));
					toggle = in ^ io[chip].lastcoins;
					io[chip].lastcoins = in;

					if (io[chip].coins_per_cred[0] > 0)
					{
						if (io[chip].credits >= 99)
						{
							WRITE_PORT(1,1);	// coin lockout
						}
						else
						{
							WRITE_PORT(1,0);	// coin lockout
							/* check if the user inserted a coin */
							if (toggle & in & 0x10)
							{
								io[chip].coins[0]++;
								WRITE_PORT(0,0x04);	// coin counter
								WRITE_PORT(0,0x0c);
								if (io[chip].coins[0] >= io[chip].coins_per_cred[0])
								{
									io[chip].credits += io[chip].creds_per_coin[0];
									io[chip].coins[0] -= io[chip].coins_per_cred[0];
								}
							}
							if (toggle & in & 0x20)
							{
								io[chip].coins[1]++;
								WRITE_PORT(0,0x08);	// coin counter
								WRITE_PORT(0,0x0c);
								if (io[chip].coins[1] >= io[chip].coins_per_cred[1])
								{
									io[chip].credits += io[chip].creds_per_coin[1];
									io[chip].coins[1] -= io[chip].coins_per_cred[1];
								}
							}
							if (toggle & in & 0x40)
							{
								io[chip].credits++;
							}
						}
					}
					else io[chip].credits = 100;	// free play

					if (io[chip].mode == 1)
					{
						int on = (cpu_getcurrentframe() & 0x10) >> 4;

						if (io[chip].credits >= 2)
							WRITE_PORT(0,0x0c | 3*on);	// lamps
						else if (io[chip].credits >= 1)
							WRITE_PORT(0,0x0c | 2*on);	// lamps
						else
							WRITE_PORT(0,0x0c);	// lamps off

						/* check for 1 player start button */
						if (toggle & in & 0x04)
						{
							if (io[chip].credits >= 1)
							{
								io[chip].credits--;
								io[chip].mode = 2;
								WRITE_PORT(0,0x0c);	// lamps off
							}
						}
						/* check for 2 players start button */
						else if (toggle & in & 0x08)
						{
							if (io[chip].credits >= 2)
							{
								io[chip].credits -= 2;
								io[chip].mode = 2;
								WRITE_PORT(0,0x0c);	// lamps off
							}
						}
					}
				}

				if (~readinputport(0) & 0x80)	/* check test mode switch */
					return 0xbb;

				return (io[chip].credits / 10) * 16 + io[chip].credits % 10;

			case 1:
				{
					int joy = READ_PORT(2) & 0x0f;
					int in,toggle;

					in = ~READ_PORT(0);
					toggle = in ^ io[chip].lastbuttons;
					io[chip].lastbuttons = (io[chip].lastbuttons & 2) | (in & 1);

					/* remap joystick */
					if (io[chip].remap_joy) joy = joy_map[joy];

					/* fire */
					joy |= ((toggle & in & 0x01)^1) << 4;
					joy |= ((in & 0x01)^1) << 5;

					return joy;
				}

			case 2:
				{
					int joy = READ_PORT(3) & 0x0f;
					int in,toggle;

					in = ~READ_PORT(0);
					toggle = in ^ io[chip].lastbuttons;
					io[chip].lastbuttons = (io[chip].lastbuttons & 1) | (in & 2);

					/* remap joystick */
					if (io[chip].remap_joy) joy = joy_map[joy];

					/* fire */
					joy |= ((toggle & in & 0x02)^2) << 3;
					joy |= ((in & 0x02)^2) << 4;

					return joy;
				}
		}
	}
}


/***************************************************************************/


UINT8 namcoio_ram[MAX_NAMCOIO * 16];

#define IORAM_READ(offset) (namcoio_ram[chip * 0x10 + (offset)] & 0x0f)
#define IORAM_WRITE(offset,data) {namcoio_ram[chip * 0x10 + (offset)] = (data) & 0x0f;}


static void handle_coins(int chip,int swap)
{
	int val,toggled;
	int credit_add = 0;
	int credit_sub = 0;
	int button;

//popmessage("%x %x %x %x %x %x %x %x",IORAM_READ(8),IORAM_READ(9),IORAM_READ(10),IORAM_READ(11),IORAM_READ(12),IORAM_READ(13),IORAM_READ(14),IORAM_READ(15));

	val = ~READ_PORT(0);	// pins 38-41
	toggled = val ^ io[chip].lastcoins;
	io[chip].lastcoins = val;

	/* check coin insertion */
	if (val & toggled & 0x01)
	{
		io[chip].coins[0]++;
		if (io[chip].coins[0] >= (io[chip].coins_per_cred[0] & 7))
		{
			credit_add = io[chip].creds_per_coin[0] - (io[chip].coins_per_cred[0] >> 3);
			io[chip].coins[0] -= io[chip].coins_per_cred[0] & 7;
		}
		else if (io[chip].coins_per_cred[0] & 8)
			credit_add = 1;
	}
	if (val & toggled & 0x02)
	{
		io[chip].coins[1]++;
		if (io[chip].coins[1] >= (io[chip].coins_per_cred[1] & 7))
		{
			credit_add = io[chip].creds_per_coin[1] - (io[chip].coins_per_cred[1] >> 3);
			io[chip].coins[1] -= io[chip].coins_per_cred[1] & 7;
		}
		else if (io[chip].coins_per_cred[1] & 8)
			credit_add = 1;
	}
	if (val & toggled & 0x08)
	{
		credit_add = 1;
	}

	val = ~READ_PORT(3);	// pins 30-33
	toggled = val ^ io[chip].lastbuttons;
	io[chip].lastbuttons = val;

	/* check start buttons, only if the game allows */
	if (IORAM_READ(9) == 0)
	// the other argument is IORAM_READ(10) = 1, meaning unknown
	{
		if (val & toggled & 0x04)
		{
			if (io[chip].credits >= 1) credit_sub = 1;
		}
		else if (val & toggled & 0x08)
		{
			if (io[chip].credits >= 2) credit_sub = 2;
		}
	}

	io[chip].credits += credit_add - credit_sub;

	IORAM_WRITE(0 ^ swap, io[chip].credits / 10);	// BCD credits
	IORAM_WRITE(1 ^ swap, io[chip].credits % 10);	// BCD credits
	IORAM_WRITE(2 ^ swap, credit_add);	// credit increment (coin inputs)
	IORAM_WRITE(3 ^ swap, credit_sub);	// credit decrement (start buttons)
	IORAM_WRITE(4, ~READ_PORT(1));	// pins 22-25
	button = ((val & 0x05) << 1) | (val & toggled & 0x05);
	IORAM_WRITE(5, button);	// pins 30 & 32 normal and impulse
	IORAM_WRITE(6, ~READ_PORT(2));	// pins 26-29
	button = (val & 0x0a) | ((val & toggled & 0x0a) >> 1);
	IORAM_WRITE(7, button);	// pins 31 & 33 normal and impulse
}



static void namco_customio_56XX_run(int chip)
{
#if VERBOSE
	logerror("execute 56XX %d mode %d\n",chip,IORAM_READ(8));
#endif

	switch (IORAM_READ(8))
	{
		case 0:	// nop?
			break;

		case 1:	// read switch inputs
			IORAM_WRITE(0, ~READ_PORT(0));	// pins 38-41
			IORAM_WRITE(1, ~READ_PORT(1));	// pins 22-25
			IORAM_WRITE(2, ~READ_PORT(2));	// pins 26-29
			IORAM_WRITE(3, ~READ_PORT(3));	// pins 30-33

//popmessage("%x %x %x %x %x %x %x %x",IORAM_READ(8),IORAM_READ(9),IORAM_READ(10),IORAM_READ(11),IORAM_READ(12),IORAM_READ(13),IORAM_READ(14),IORAM_READ(15));

			WRITE_PORT(0,IORAM_READ(9));	// output to pins 13-16 (motos, pacnpal, gaplus)
			WRITE_PORT(1,IORAM_READ(10));	// output to pins 17-20 (gaplus)
			break;

		case 2:	// initialize coinage settings
			io[chip].coins_per_cred[0] = IORAM_READ(9);
			io[chip].creds_per_coin[0] = IORAM_READ(10);
			io[chip].coins_per_cred[1] = IORAM_READ(11);
			io[chip].creds_per_coin[1] = IORAM_READ(12);
			// IORAM_READ(13) = 1; meaning unknown - possibly a 3rd coin input? (there's a IPT_UNUSED bit in port A)
			// IORAM_READ(14) = 1; meaning unknown - possibly a 3rd coin input? (there's a IPT_UNUSED bit in port A)
			// IORAM_READ(15) = 0; meaning unknown
			break;

		case 4:	// druaga, digdug chip #1: read dip switches and inputs
				// superpac chip #0: process coin and start inputs, read switch inputs
			handle_coins(chip,0);
			break;

		case 7:	// bootup check (liblrabl only)
			{
				// liblrabl chip #1: 9-15 = f 1 2 3 4 0 0, expects 2 = e
				// liblrabl chip #2: 9-15 = 0 1 4 5 5 0 0, expects 7 = 6
				IORAM_WRITE(2,0xe);
				IORAM_WRITE(7,0x6);
			}
			break;

		case 8:	// bootup check
			{
				int i,sum;

				// superpac: 9-15 = f f f f f f f, expects 0-1 = 6 9. 0x69 = f+f+f+f+f+f+f.
				// motos:    9-15 = f f f f f f f, expects 0-1 = 6 9. 0x69 = f+f+f+f+f+f+f.
				// phozon:   9-15 = 1 2 3 4 5 6 7, expects 0-1 = 1 c. 0x1c = 1+2+3+4+5+6+7
				sum = 0;
				for (i = 9;i < 16;i++)
					sum += IORAM_READ(i);
				IORAM_WRITE(0,sum >> 4);
				IORAM_WRITE(1,sum & 0xf);
			}
			break;

		case 9:	// read dip switches and inputs
			WRITE_PORT(0,0);	// set pin 13 = 0
			IORAM_WRITE(0, ~READ_PORT(0));	// pins 38-41, pin 13 = 0
			IORAM_WRITE(2, ~READ_PORT(1));	// pins 22-25, pin 13 = 0
			IORAM_WRITE(4, ~READ_PORT(2));	// pins 26-29, pin 13 = 0
			IORAM_WRITE(6, ~READ_PORT(3));	// pins 30-33, pin 13 = 0
			WRITE_PORT(0,1);	// set pin 13 = 1
			IORAM_WRITE(1, ~READ_PORT(0));	// pins 38-41, pin 13 = 1
			IORAM_WRITE(3, ~READ_PORT(1));	// pins 22-25, pin 13 = 1
			IORAM_WRITE(5, ~READ_PORT(2));	// pins 26-29, pin 13 = 1
			IORAM_WRITE(7, ~READ_PORT(3));	// pins 30-33, pin 13 = 1
			break;

		default:
			logerror("Namco I/O %d: unknown I/O mode %d\n",chip,IORAM_READ(8));
	}
}



static void namco_customio_59XX_run(int chip)
{
#if VERBOSE
	logerror("execute 59XX %d mode %d\n",chip,IORAM_READ(8));
#endif

	switch (IORAM_READ(8))
	{
		case 0:	// nop?
			break;

		case 3:	// pacnpal chip #1: read dip switches and inputs
			IORAM_WRITE(4, ~READ_PORT(0));	// pins 38-41, pin 13 = 0 ?
			IORAM_WRITE(5, ~READ_PORT(2));	// pins 26-29 ?
			IORAM_WRITE(6, ~READ_PORT(1));	// pins 22-25 ?
			IORAM_WRITE(7, ~READ_PORT(3));	// pins 30-33
			break;

		default:
			logerror("Namco I/O %d: unknown I/O mode %d\n",chip,IORAM_READ(8));
	}
}



static void namco_customio_58XX_run(int chip)
{
#if VERBOSE
	logerror("execute 58XX %d mode %d\n",chip,IORAM_READ(8));
#endif

	switch (IORAM_READ(8))
	{
		case 0:	// nop?
			break;

		case 1:	// read switch inputs
			IORAM_WRITE(4, ~READ_PORT(0));	// pins 38-41
			IORAM_WRITE(5, ~READ_PORT(1));	// pins 22-25
			IORAM_WRITE(6, ~READ_PORT(2));	// pins 26-29
			IORAM_WRITE(7, ~READ_PORT(3));	// pins 30-33

//popmessage("%x %x %x %x %x %x %x %x",IORAM_READ(8),IORAM_READ(9),IORAM_READ(10),IORAM_READ(11),IORAM_READ(12),IORAM_READ(13),IORAM_READ(14),IORAM_READ(15));

			WRITE_PORT(0,IORAM_READ(9));	// output to pins 13-16 (toypop)
			WRITE_PORT(1,IORAM_READ(10));	// output to pins 17-20 (toypop)
			break;

		case 2:	// initialize coinage settings
			io[chip].coins_per_cred[0] = IORAM_READ(9);
			io[chip].creds_per_coin[0] = IORAM_READ(10);
			io[chip].coins_per_cred[1] = IORAM_READ(11);
			io[chip].creds_per_coin[1] = IORAM_READ(12);
			// IORAM_READ(13) = 1; meaning unknown - possibly a 3rd coin input? (there's a IPT_UNUSED bit in port A)
			// IORAM_READ(14) = 0; meaning unknown - possibly a 3rd coin input? (there's a IPT_UNUSED bit in port A)
			// IORAM_READ(15) = 0; meaning unknown
			break;

		case 3:	// process coin and start inputs, read switch inputs
			handle_coins(chip,2);
			break;

		case 4:	// read dip switches and inputs
			WRITE_PORT(0,0);	// set pin 13 = 0
			IORAM_WRITE(0, ~READ_PORT(0));	// pins 38-41, pin 13 = 0
			IORAM_WRITE(2, ~READ_PORT(1));	// pins 22-25, pin 13 = 0
			IORAM_WRITE(4, ~READ_PORT(2));	// pins 26-29, pin 13 = 0
			IORAM_WRITE(6, ~READ_PORT(3));	// pins 30-33, pin 13 = 0
			WRITE_PORT(0,1);	// set pin 13 = 1
			IORAM_WRITE(1, ~READ_PORT(0));	// pins 38-41, pin 13 = 1
			IORAM_WRITE(3, ~READ_PORT(1));	// pins 22-25, pin 13 = 1
			IORAM_WRITE(5, ~READ_PORT(2));	// pins 26-29, pin 13 = 1
			IORAM_WRITE(7, ~READ_PORT(3));	// pins 30-33, pin 13 = 1
			break;

		case 5:	// bootup check
			/* mode 5 values are checked against these numbers during power up
               mappy:  9-15 = 3 6 5 f a c e, expects 1-7 =   8 4 6 e d 9 d
               grobda: 9-15 = 2 3 4 5 6 7 8, expects 2 = f and 6 = c
               phozon: 9-15 = 0 1 2 3 4 5 6, expects 0-7 = 0 2 3 4 5 6 c a
               gaplus: 9-15 = f f f f f f f, expects 0-1 = f f

               This has been determined to be the result of repeated XORs,
               controlled by a 7-bit LFSR. The following algorithm should be
               equivalent to the original one (though probably less efficient).
               The first nibble of the result however is uncertain. It is usually
               0, but in some cases it toggles between 0 and F. We use a kludge
               to give Gaplus the F it expects.
            */
			{
				int i,n,rng,seed;
				#define NEXT(n) ((((n) & 1) ? (n) ^ 0x90 : (n)) >> 1)

				/* initialize the LFSR depending on the first two arguments */
				n = (IORAM_READ(9) * 16 + IORAM_READ(10)) & 0x7f;
				seed = 0x22;
				for (i = 0;i < n;i++)
					seed = NEXT(seed);

				/* calculate the answer */
				for (i = 1;i < 8;i++)
				{
					n = 0;
					rng = seed;
					if (rng & 1) { n ^= ~IORAM_READ(11); }
					rng = NEXT(rng);
					seed = rng;	// save state for next loop
					if (rng & 1) { n ^= ~IORAM_READ(10); }
					rng = NEXT(rng);
					if (rng & 1) { n ^= ~IORAM_READ(9); }
					rng = NEXT(rng);
					if (rng & 1) { n ^= ~IORAM_READ(15); }
					rng = NEXT(rng);
					if (rng & 1) { n ^= ~IORAM_READ(14); }
					rng = NEXT(rng);
					if (rng & 1) { n ^= ~IORAM_READ(13); }
					rng = NEXT(rng);
					if (rng & 1) { n ^= ~IORAM_READ(12); }

					IORAM_WRITE(i,~n);
				}
				IORAM_WRITE(0,0x0);
				/* kludge for gaplus */
				if (IORAM_READ(9) == 0xf) IORAM_WRITE(0,0xf);
			}
			break;

		default:
			logerror("Namco I/O %d: unknown I/O mode %d\n",chip,IORAM_READ(8));
	}
}



READ8_HANDLER( namcoio_r )
{
	// RAM is 4-bit wide; Pac & Pal requires the | 0xf0 otherwise Easter egg doesn't work
	offset &= 0x3f;

#if VERBOSE
	logerror("%04x: I/O read %d: mode %d, offset %d = %02x\n", activecpu_get_pc(), offset / 16, namcoio_ram[(offset & 0x30) + 8], offset & 0x0f, namcoio_ram[offset]&0x0f);
#endif

	return 0xf0 | namcoio_ram[offset];
}

WRITE8_HANDLER( namcoio_w )
{
	offset &= 0x3f;
	data &= 0x0f;	// RAM is 4-bit wide

#if VERBOSE
	logerror("%04x: I/O write %d: offset %d = %02x\n", activecpu_get_pc(), offset / 16, offset & 0x0f, data);
#endif

	namcoio_ram[offset] = data;
}

void namcoio_set_reset_line(int chipnum, int state)
{
	io[chipnum].reset = (state == ASSERT_LINE) ? 1 : 0;
	if (state != CLEAR_LINE)
	{
		/* reset internal registers */
		io[chipnum].credits = 0;
		io[chipnum].coins[0] = 0;
		io[chipnum].coins_per_cred[0] = 1;
		io[chipnum].creds_per_coin[0] = 1;
		io[chipnum].coins[1] = 0;
		io[chipnum].coins_per_cred[1] = 1;
		io[chipnum].creds_per_coin[1] = 1;
		io[chipnum].in_count = 0;
	}
}

static void namcoio_run(int param)
{
	switch (io[param].type)
	{
		case NAMCOIO_56XX:
			namco_customio_56XX_run(param);
			break;
		case NAMCOIO_58XX:
			namco_customio_58XX_run(param);
			break;
		case NAMCOIO_59XX:
			namco_customio_59XX_run(param);
			break;
	}
}

void namcoio_set_irq_line(int chipnum, int state)
{
	if (chipnum < MAX_NAMCOIO && state != CLEAR_LINE && !io[chipnum].reset)
	{
		/* give the cpu a tiny bit of time to write the command before processing it */
		mame_timer_set(MAME_TIME_IN_USEC(50), chipnum, namcoio_run);
	}
}

static void namcoio_state_save(int chipnum)
{

	state_save_register_item_pointer("namcoio", chipnum, ((UINT8 *) (&namcoio_ram[chipnum * 16])), 16);
	state_save_register_item("namcoio", chipnum, io[chipnum].reset);
	state_save_register_item("namcoio", chipnum, io[chipnum].lastcoins);
	state_save_register_item("namcoio", chipnum, io[chipnum].lastbuttons);
	state_save_register_item("namcoio", chipnum, io[chipnum].credits);
	state_save_register_item_array("namcoio", chipnum, io[chipnum].coins);
	state_save_register_item_array("namcoio", chipnum, io[chipnum].coins_per_cred);
	state_save_register_item_array("namcoio", chipnum, io[chipnum].creds_per_coin);
	state_save_register_item("namcoio", chipnum, io[chipnum].in_count);
	state_save_register_item("namcoio", chipnum, io[chipnum].mode);
	state_save_register_item("namcoio", chipnum, io[chipnum].coincred_mode);
	state_save_register_item("namcoio", chipnum, io[chipnum].remap_joy);
}

void namcoio_init(int chipnum, int type, const struct namcoio_interface *intf)
{
	if (chipnum < MAX_NAMCOIO)
	{
		io[chipnum].type = type;
		io[chipnum].in[0] = (intf && intf->in[0]) ? intf->in[0] : nop_r;
		io[chipnum].in[1] = (intf && intf->in[1]) ? intf->in[1] : nop_r;
		io[chipnum].in[2] = (intf && intf->in[2]) ? intf->in[2] : nop_r;
		io[chipnum].in[3] = (intf && intf->in[3]) ? intf->in[3] : nop_r;
		io[chipnum].out[0] = (intf && intf->out[0]) ? intf->out[0] : nop_w;
		io[chipnum].out[1] = (intf && intf->out[1]) ? intf->out[1] : nop_w;
		namcoio_state_save(chipnum);
		namcoio_set_reset_line(chipnum,PULSE_LINE);
	}
}







static void nmi_generate(int param)
{
	if (!cpunum_is_suspended(param, SUSPEND_REASON_HALT | SUSPEND_REASON_RESET | SUSPEND_REASON_DISABLE))
	{
#if VERBOSE
	logerror("NMI cpu %d\n",nmi_cpu[param]);
#endif

		cpunum_set_input_line(nmi_cpu[param], INPUT_LINE_NMI, PULSE_LINE);
	}
#if VERBOSE
	else
		logerror("NMI not generated because cpu %d is suspended\n",nmi_cpu[param]);
#endif
}

static UINT8 customio_command[MAX_06XX];

static void namco_06xx_state_save(int chipnum)
{

		//state_save_register_item("namcoio06xx", chipnum, nmi_cpu[chipnum]);
		state_save_register_item("namcoio06xx", chipnum, customio_command[chipnum]);
}


void namco_06xx_init(int chipnum, int cpu,
	int type0, const struct namcoio_interface *intf0,
	int type1, const struct namcoio_interface *intf1,
	int type2, const struct namcoio_interface *intf2,
	int type3, const struct namcoio_interface *intf3)
{
	if (chipnum < MAX_06XX)
	{
		namcoio_init(4*chipnum + 0, type0, intf0);
		namcoio_init(4*chipnum + 1, type1, intf1);
		namcoio_init(4*chipnum + 2, type2, intf2);
		namcoio_init(4*chipnum + 3, type3, intf3);
		nmi_cpu[chipnum] = cpu;
		nmi_timer[chipnum] = mame_timer_alloc(nmi_generate);
		namco_06xx_state_save(chipnum);
	}
}



static UINT8 namcoio_53XX_digdug_read(int chip)
{
#if VERBOSE
	logerror("%04x: custom 53XX read\n",activecpu_get_pc());
#endif

	switch ((io[chip].in_count++) % 2)
	{
		default:
		case 0: return READ_PORT(0) | (READ_PORT(1) << 4);
		case 1: return READ_PORT(2) | (READ_PORT(3) << 4);
	}
}


static UINT8 namcoio_53XX_polepos_read(int chip)
{
#if VERBOSE
	logerror("%04x: custom 53XX read\n",activecpu_get_pc());
#endif

	switch ((io[chip].in_count++) % 8)
	{
		case 0: return READ_PORT(0) | (READ_PORT(1) << 4);	// steering
		case 4: return READ_PORT(2) | (READ_PORT(3) << 4);	// dip switches
		default: return 0xff;	// polepos2 hangs if 0 is returned
	}
}


static UINT8 namco_06xx_data_read(int chipnum)
{
#if VERBOSE
	logerror("forwarding read to chip %d\n",chipnum%3);
#endif

	switch (io[chipnum].type)
	{
		case NAMCOIO_50XX:   return namco_50xx_read();
		case NAMCOIO_50XX_2: return namco_50xx_2_read();
		case NAMCOIO_51XX: return namcoio_51XX_read(chipnum);
		case NAMCOIO_53XX_DIGDUG:  return namcoio_53XX_digdug_read(chipnum);
		case NAMCOIO_53XX_POLEPOS: return namcoio_53XX_polepos_read(chipnum);
		default:
			logerror("%04x: custom IO type %d unsupported read\n",activecpu_get_pc(),io[chipnum].type);
			return 0xff;
	}
}


static void namco_06xx_data_write(int chipnum,UINT8 data)
{
#if VERBOSE
	logerror("forwarding write to chip %d\n",chipnum%3);
#endif

	switch (io[chipnum].type)
	{
		case NAMCOIO_50XX:   namco_50xx_write(data); break;
		case NAMCOIO_50XX_2: namco_50xx_2_write(data); break;
		case NAMCOIO_51XX:   namcoio_51XX_write(chipnum,data); break;
		case NAMCOIO_52XX:   namcoio_52XX_write(data); break;
		case NAMCOIO_54XX:   namco_54xx_write(data); break;
		default:
			logerror("%04x: custom IO type %d unsupported write\n",activecpu_get_pc(),io[chipnum].type);
			break;
	}
}


static void namco_06xx_read_request(int chipnum)
{
#if VERBOSE
	logerror("requesting read to chip %d\n",chipnum%3);
#endif

	switch (io[chipnum].type)
	{
		case NAMCOIO_50XX:   namco_50xx_read_request(); break;
		case NAMCOIO_50XX_2: namco_50xx_2_read_request(); break;
		default:
			logerror("%04x: custom IO type %d read_request unsupported\n",activecpu_get_pc(),io[chipnum].type);
			break;
	}
}


static UINT8 namco_06xx_data_r(int chip,int offset)
{
#if VERBOSE
	logerror("%04x: 06XX #%d read offset %d\n",activecpu_get_pc(),chip,offset);
#endif

	if (!(customio_command[chip] & 0x10))
	{
		logerror("%04x: 06XX #%d read in write mode %02x\n",activecpu_get_pc(),chip,customio_command[chip]);
		return 0;
	}

	switch (customio_command[chip] & 0xf)
	{
		case 0x1: return namco_06xx_data_read(4*chip + 0); break;
		case 0x2: return namco_06xx_data_read(4*chip + 1); break;
		case 0x4: return namco_06xx_data_read(4*chip + 2); break;
		case 0x8: return namco_06xx_data_read(4*chip + 3); break;
		default:
			logerror("%04x: 06XX #%d read in unsupported mode %02x\n",activecpu_get_pc(),chip,customio_command[chip]);
			return 0xff;
	}
}


static void namco_06xx_data_w(int chip,int offset,int data)
{
#if VERBOSE
	logerror("%04x: 06XX #%d write offset %d = %02x\n",activecpu_get_pc(),chip,offset,data);
#endif

	if (customio_command[chip] & 0x10)
	{
		logerror("%04x: 06XX #%d write in read mode %02x\n",activecpu_get_pc(),chip,customio_command[chip]);
		return;
	}

	switch (customio_command[chip] & 0xf)
	{
		case 0x1: namco_06xx_data_write(4*chip + 0,data); break;
		case 0x2: namco_06xx_data_write(4*chip + 1,data); break;
		case 0x4: namco_06xx_data_write(4*chip + 2,data); break;
		case 0x8: namco_06xx_data_write(4*chip + 3,data); break;
		default:
			logerror("%04x: 06XX #%d write in unsupported mode %02x\n",activecpu_get_pc(),chip,customio_command[chip]);
			break;
	}
}


static UINT8 namco_06xx_ctrl_r(int chip)
{
#if VERBOSE
	logerror("%04x: 06XX #%d ctrl_r\n",activecpu_get_pc(),chip);
#endif
	return customio_command[chip];
}

static void namco_06xx_ctrl_w(int chip,int data)
{
#if VERBOSE
	logerror("%04x: 06XX #%d command %02x\n",activecpu_get_pc(),chip,data);
#endif

	customio_command[chip] = data;

	if ((customio_command[chip] & 0x0f) == 0)
	{
#if VERBOSE
		logerror("disabling nmi generate timer\n");
#endif
		mame_timer_adjust(nmi_timer[chip], time_never, chip, time_never);
	}
	else
	{
#if VERBOSE
		logerror("setting nmi generate timer to 200us\n");
#endif
		// this timing is critical. Due to a bug, Bosconian will stop responding to
		// inputs if a transfer terminates at the wrong time.
		// On the other hand, the time cannot be too short otherwise the 54XX will
		// not have enough time to process the incoming commands.
		mame_timer_adjust(nmi_timer[chip], MAME_TIME_IN_USEC(200), chip, MAME_TIME_IN_USEC(200));

		if (customio_command[chip] & 0x10)
		{
			switch (customio_command[chip] & 0xf)
			{
				case 0x1: namco_06xx_read_request(4*chip + 0); break;
				case 0x2: namco_06xx_read_request(4*chip + 1); break;
				case 0x4: namco_06xx_read_request(4*chip + 2); break;
				case 0x8: namco_06xx_read_request(4*chip + 3); break;
				default:
					logerror("%04x: 06XX #%d read in unsupported mode %02x\n",activecpu_get_pc(),chip,customio_command[chip]);
			}
		}
	}
}



READ8_HANDLER( namco_06xx_0_data_r )		{ return namco_06xx_data_r(0,offset); }
READ8_HANDLER( namco_06xx_1_data_r )		{ return namco_06xx_data_r(1,offset); }
WRITE8_HANDLER( namco_06xx_0_data_w )	{ namco_06xx_data_w(0,offset,data); }
WRITE8_HANDLER( namco_06xx_1_data_w )	{ namco_06xx_data_w(1,offset,data); }
READ8_HANDLER( namco_06xx_0_ctrl_r )		{ return namco_06xx_ctrl_r(0); }
READ8_HANDLER( namco_06xx_1_ctrl_r )		{ return namco_06xx_ctrl_r(1); }
WRITE8_HANDLER( namco_06xx_0_ctrl_w )	{ namco_06xx_ctrl_w(0,data); }
WRITE8_HANDLER( namco_06xx_1_ctrl_w )	{ namco_06xx_ctrl_w(1,data); }
