mame/src/devices/machine/mm5740.cpp

// license:BSD-3-Clause
// copyright-holders:R. Belmont, Mark Garlanger
/**********************************************************************

    National Semiconductor MM5740 Keyboard Encoder emulation
    (Code originally based on kb3600.cpp)

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

#include "emu.h"
#include "mm5740.h"

#include <algorithm>


//**************************************************************************
//  GLOBAL VARIABLES
//**************************************************************************

// devices
const device_type MM5740 = device_creator<mm5740_device>;

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

ROM_START( mm5740 )
	ROM_REGION(0x1c2, "internal", 0)
	ROM_LOAD("mm5740aac.ic1", 0x000, 0x1c2, CRC(aed404d3) SHA1(e7b9feba5f789f388d27820b5f3fa591d41b4ab1))
ROM_END

//-------------------------------------------------
//  rom_region - device-specific ROM region
//-------------------------------------------------

const tiny_rom_entry *mm5740_device::device_rom_region() const
{
	return ROM_NAME( mm5740 );
}


//-------------------------------------------------
//  mm5740_device - constructor
//-------------------------------------------------

mm5740_device::mm5740_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
	device_t(mconfig, MM5740, "MM5740", tag, owner, clock, "mm5740", __FILE__),
	m_read_x{{*this}, {*this}, {*this}, {*this}, {*this}, {*this}, {*this}, {*this}, {*this}},
	m_read_shift(*this),
	m_read_control(*this),
	m_write_data_ready(*this),
	m_rom(*this, "internal")
{
	std::fill_n(m_x_mask, 9, 0);
}

uint32_t mm5740_device::calc_effective_clock_key_debounce(uint32_t capacitance)
{
	// calculate key debounce based on capacitance in pF
	uint32_t key_debounce_msec = capacitance / 125;
	if (key_debounce_msec == 0)
	{
		key_debounce_msec = 1;
	}

	return 1000 / key_debounce_msec;
}

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

void mm5740_device::device_start()
{
	// resolve callbacks
	for(int i = 0; i < 9; i++)
	{
		m_read_x[i].resolve_safe(0x3ff);
	}
	m_read_shift.resolve_safe(0);
	m_read_control.resolve_safe(0);
	m_write_data_ready.resolve_safe();

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

	// state saving
	save_item(NAME(m_b));
	save_item(NAME(m_x_mask));
}


//-------------------------------------------------
//  device_start - device-specific reset
//-------------------------------------------------

void mm5740_device::device_reset()
{
}

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

void mm5740_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr)
{
	int ako = 0;

	for (int x = 0; x < 9; x++)
	{
		uint16_t data = m_read_x[x]() ^ 0x3ff;

		if ((data ^ m_x_mask[x]) == 0)
		{
			// bail early if nothing has changed.
			continue;
		}

		for (int y = 0; y < 10; y++)
		{

			if (BIT(data, y))
			{
				uint8_t *rom = m_rom->base();
				uint16_t offset = x*10 + y;
				// Common portion
				uint16_t common = (uint16_t) rom[offset];

				offset += (((m_read_shift() ? 1: 0) + (m_read_control() ? 2: 0)) + 1) * 90;

				// Unique portion based on shift/ctrl keys.
				uint8_t uniq = rom[offset];

				uint16_t b = (((common & 0x10) << 4) | ((uniq & 0x0f) << 4) | (common & 0x0f)) ^ 0x1ff;

				ako = 1;

				if (!BIT(m_x_mask[x], y))
				{
					m_x_mask[x] |= (1 << y);
					if (m_b != b)
					{
						m_b = b;
						m_write_data_ready(ASSERT_LINE);

						return;
					}
				}
			}
			else    // key released, unmark it from the "down" info
			{
				m_x_mask[x] &= ~(1 << y);
			}
		}
	}

	if (!ako)
	{
		m_write_data_ready(CLEAR_LINE);
		m_b = -1;
	}
}


//-------------------------------------------------
//  b_r -
//-------------------------------------------------

uint16_t mm5740_device::b_r()
{
	m_write_data_ready(CLEAR_LINE);
	return m_b;
}