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

  machine.c

  Functions to emulate general aspects of the machine (RAM, ROM, interrupts,
  I/O ports)

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

#include "driver.h"
#include "includes/lkage.h"


static UINT8 from_main,from_mcu;
static int mcu_sent = 0,main_sent = 0;


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

 Legend of Kage 68705 protection interface

 The following is ENTIRELY GUESSWORK!!!
 And moreover, the game seems to work anyway regardless of what the mcu returns.

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

static UINT8 portA_in,portA_out,ddrA;

READ8_HANDLER( lkage_68705_portA_r )
{
//logerror("%04x: 68705 port A read %02x\n",cpu_get_pc(space->cpu),portA_in);
	return (portA_out & ddrA) | (portA_in & ~ddrA);
}

WRITE8_HANDLER( lkage_68705_portA_w )
{
//logerror("%04x: 68705 port A write %02x\n",cpu_get_pc(space->cpu),data);
	portA_out = data;
}

WRITE8_HANDLER( lkage_68705_ddrA_w )
{
	ddrA = data;
}



/*
 *  Port B connections:
 *
 *  all bits are logical 1 when read (+5V pullup)
 *
 *  1   W  when 1->0, enables latch which brings the command from main CPU (read from port A)
 *  2   W  when 0->1, copies port A to the latch for the main CPU
 */

static UINT8 portB_in,portB_out,ddrB;

READ8_HANDLER( lkage_68705_portB_r )
{
	return (portB_out & ddrB) | (portB_in & ~ddrB);
}

WRITE8_HANDLER( lkage_68705_portB_w )
{
//logerror("%04x: 68705 port B write %02x\n",cpu_get_pc(space->cpu),data);

	if ((ddrB & 0x02) && (~data & 0x02) && (portB_out & 0x02))
	{
		portA_in = from_main;
		if (main_sent) cputag_set_input_line(space->machine, "mcu", 0, CLEAR_LINE);
		main_sent = 0;
logerror("read command %02x from main cpu\n",portA_in);
	}
	if ((ddrB & 0x04) && (data & 0x04) && (~portB_out & 0x04))
	{
logerror("send command %02x to main cpu\n",portA_out);
		from_mcu = portA_out;
		mcu_sent = 1;
	}

	portB_out = data;
}

WRITE8_HANDLER( lkage_68705_ddrB_w )
{
	ddrB = data;
}


static UINT8 portC_in,portC_out,ddrC;

READ8_HANDLER( lkage_68705_portC_r )
{
	portC_in = 0;
	if (main_sent) portC_in |= 0x01;
	if (!mcu_sent) portC_in |= 0x02;
//logerror("%04x: 68705 port C read %02x\n",cpu_get_pc(space->cpu),portC_in);
	return (portC_out & ddrC) | (portC_in & ~ddrC);
}

WRITE8_HANDLER( lkage_68705_portC_w )
{
logerror("%04x: 68705 port C write %02x\n",cpu_get_pc(space->cpu),data);
	portC_out = data;
}

WRITE8_HANDLER( lkage_68705_ddrC_w )
{
	ddrC = data;
}


WRITE8_HANDLER( lkage_mcu_w )
{
logerror("%04x: mcu_w %02x\n",cpu_get_pc(space->cpu),data);
	from_main = data;
	main_sent = 1;
	cputag_set_input_line(space->machine, "mcu", 0, ASSERT_LINE);
}

READ8_HANDLER( lkage_mcu_r )
{
logerror("%04x: mcu_r %02x\n",cpu_get_pc(space->cpu),from_mcu);
	mcu_sent = 0;
	return from_mcu;
}

READ8_HANDLER( lkage_mcu_status_r )
{
	int res = 0;

	/* bit 0 = when 1, mcu is ready to receive data from main cpu */
	/* bit 1 = when 1, mcu has sent data to the main cpu */
//logerror("%04x: mcu_status_r\n",cpu_get_pc(space->cpu));
	if (!main_sent) res |= 0x01;
	if (mcu_sent) res |= 0x02;

	return res;
}
