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

    MM74C922/MM74C923 16/20-Key Encoder emulation

    Copyright MESS Team.
    Visit http://mamedev.org for licensing and usage restrictions.

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

#include "mm74c922.h"
#include "machine/devhelpr.h"



//**************************************************************************
//  MACROS / CONSTANTS
//**************************************************************************

#define LOG 1



//**************************************************************************
//  DEVICE DEFINITIONS
//**************************************************************************

const device_type MM74C922 = &device_creator<mm74c922_device>;
const device_type MM74C923 = &device_creator<mm74c922_device>;



//**************************************************************************
//  INLINE HELPERS
//**************************************************************************

//-------------------------------------------------
//  change_output_lines -
//-------------------------------------------------

inline void mm74c922_device::change_output_lines()
{
	if (m_next_da != m_da)
	{
		m_da = m_next_da;

		if (LOG) logerror("MM74C922 '%s' Data Available: %u\n", tag(), m_da);

		m_out_da_func(m_da);
	}
}


//-------------------------------------------------
//  clock_scan_counters -
//-------------------------------------------------

inline void mm74c922_device::clock_scan_counters()
{
	if (!m_inhibit)
	{
		m_x++;
		m_x &= 0x03;
	}
}


//-------------------------------------------------
//  device_start - device-specific startup
//-------------------------------------------------

inline void mm74c922_device::detect_keypress()
{
	if (m_inhibit)
	{
		UINT8 data = m_in_x_func[m_x](0);

		if (BIT(data, m_y))
		{
			// key released
			m_inhibit = 0;
			m_next_da = 0;
			m_data = 0xff; // high-Z

			if (LOG) logerror("MM74C922 '%s' Key Released\n", tag());
		}
	}
	else
	{
		UINT8 data = m_in_x_func[m_x](0);

		for (int y = 0; y < m_max_y; y++)
		{
			if (!BIT(data, y))
			{
				// key depressed
				m_inhibit = 1;
				m_next_da = 1;
				m_y = y;

				m_data = (y << 2) | m_x;

				if (LOG) logerror("MM74C922 '%s' Key Depressed: X %u Y %u = %02x\n", tag(), m_x, y, m_data);
				return;
			}
		}
	}
}


//**************************************************************************
//  LIVE DEVICE
//**************************************************************************

//-------------------------------------------------
//  mm74c922_device - constructor
//-------------------------------------------------

mm74c922_device::mm74c922_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
    : device_t(mconfig, MM74C922, "MM74C922", tag, owner, clock),
	  m_x(0),
	  m_y(0),
	  m_next_da(0)
{
}


//-------------------------------------------------
//  static_set_config - configuration helper
//-------------------------------------------------

void mm74c922_device::static_set_config(device_t &device, int max_y)
{
	mm74c922_device &mm74c922 = downcast<mm74c922_device &>(device);

	mm74c922.m_max_y = max_y;
}


//-------------------------------------------------
//  device_config_complete - perform any
//  operations now that the configuration is
//  complete
//-------------------------------------------------

void mm74c922_device::device_config_complete()
{
	// inherit a copy of the static data
	const mm74c922_interface *intf = reinterpret_cast<const mm74c922_interface *>(static_config());
	if (intf != NULL)
		*static_cast<mm74c922_interface *>(this) = *intf;

	// or initialize to defaults if none provided
	else
	{
		memset(&m_out_da_cb, 0, sizeof(m_out_da_cb));
		memset(&m_in_x1_cb, 0, sizeof(m_in_x1_cb));
		memset(&m_in_x2_cb, 0, sizeof(m_in_x2_cb));
		memset(&m_in_x3_cb, 0, sizeof(m_in_x3_cb));
		memset(&m_in_x4_cb, 0, sizeof(m_in_x4_cb));
		memset(&m_in_x5_cb, 0, sizeof(m_in_x5_cb));
	}
}


//-------------------------------------------------
//  device_start - device-specific startup
//-------------------------------------------------

void mm74c922_device::device_start()
{
	// resolve callbacks
	m_out_da_func.resolve(m_out_da_cb, *this);
	m_in_x_func[0].resolve(m_in_x1_cb, *this);
	m_in_x_func[1].resolve(m_in_x2_cb, *this);
	m_in_x_func[2].resolve(m_in_x3_cb, *this);
	m_in_x_func[3].resolve(m_in_x4_cb, *this);
	m_in_x_func[4].resolve(m_in_x5_cb, *this);

	// set initial values
	change_output_lines();

	// allocate timers
	m_scan_timer = timer_alloc();
	m_scan_timer->adjust(attotime::zero, 0, attotime::from_hz(50));

	// register for state saving
	save_item(NAME(m_inhibit));
	save_item(NAME(m_x));
	save_item(NAME(m_y));
	save_item(NAME(m_data));
	save_item(NAME(m_da));
	save_item(NAME(m_next_da));
}


//-------------------------------------------------
//  device_timer - handler timer events
//-------------------------------------------------

void mm74c922_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr)
{
	change_output_lines();
	clock_scan_counters();
	detect_keypress();
}


//-------------------------------------------------
//  data_out_r -
//-------------------------------------------------

UINT8 mm74c922_device::data_out_r()
{
	if (LOG) logerror("MM74C922 '%s' Data Read: %02x\n", tag(), m_data);

	return m_data;
}