#include "driver.h"
#include "cpu/z80/z80.h"


static unsigned char from_main,from_mcu;
static int mcu_sent = 0,main_sent = 0;


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

 Return of Invaders 68705 protection interface

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

static unsigned char portA_in,portA_out,ddrA;

READ8_HANDLER( retofinv_68705_portA_r )
{
/*logerror("%04x: 68705 port A read %02x\n",activecpu_get_pc(),portA_in); */
	return (portA_out & ddrA) | (portA_in & ~ddrA);
}

WRITE8_HANDLER( retofinv_68705_portA_w )
{
/*logerror("%04x: 68705 port A write %02x\n",activecpu_get_pc(),data); */
	portA_out = data;
}

WRITE8_HANDLER( retofinv_68705_ddrA_w )
{
	ddrA = data;
}



/*
 *  Port B connections:
 *
 *  all bits are logical 1 when read (+5V pullup)
 *
 *  1   W  IRQ ack and enable latch which holds data from main Z80 memory
 *  2   W  loads latch to Z80
 */

static unsigned char portB_in,portB_out,ddrB;

READ8_HANDLER( retofinv_68705_portB_r )
{
	return (portB_out & ddrB) | (portB_in & ~ddrB);
}

WRITE8_HANDLER( retofinv_68705_portB_w )
{
/*logerror("%04x: 68705 port B write %02x\n",activecpu_get_pc(),data); */

	if ((ddrB & 0x02) && (~data & 0x02) && (portB_out & 0x02))
	{
		portA_in = from_main;
		if (main_sent) cpunum_set_input_line(3,0,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( retofinv_68705_ddrB_w )
{
	ddrB = data;
}


/*
 *  Port C connections:
 *
 *  all bits are logical 1 when read (+5V pullup)
 *
 *  0   R  1 when pending command Z80->68705
 *  1   R  0 when pending command 68705->Z80
 */

static unsigned char portC_in,portC_out,ddrC;

READ8_HANDLER( retofinv_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",activecpu_get_pc(),portC_in); */
	return (portC_out & ddrC) | (portC_in & ~ddrC);
}

WRITE8_HANDLER( retofinv_68705_portC_w )
{
logerror("%04x: 68705 port C write %02x\n",activecpu_get_pc(),data);
	portC_out = data;
}

WRITE8_HANDLER( retofinv_68705_ddrC_w )
{
	ddrC = data;
}


WRITE8_HANDLER( retofinv_mcu_w )
{
logerror("%04x: mcu_w %02x\n",activecpu_get_pc(),data);
	from_main = data;
	main_sent = 1;
	cpunum_set_input_line(3,0,ASSERT_LINE);
}

READ8_HANDLER( retofinv_mcu_r )
{
logerror("%04x: mcu_r %02x\n",activecpu_get_pc(),from_mcu);
	mcu_sent = 0;
	return from_mcu;
}

READ8_HANDLER( retofinv_mcu_status_r )
{
	int res = 0;

	/* bit 4 = when 1, mcu is ready to receive data from main cpu */
	/* bit 5 = when 1, mcu has sent data to the main cpu */
/*logerror("%04x: mcu_status_r\n",activecpu_get_pc()); */
	if (!main_sent) res |= 0x10;
	if (mcu_sent) res |= 0x20;

	return res;
}
