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-rw-r--r--src/emu/drivers/xtal.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/src/emu/drivers/xtal.h b/src/emu/drivers/xtal.h
index 862fc5a0a6c..8c9fb948510 100644
--- a/src/emu/drivers/xtal.h
+++ b/src/emu/drivers/xtal.h
@@ -58,6 +58,7 @@ enum
XTAL_1MHz = 1000000, /* Used to drive OKI M6295 chips */
XTAL_1_2944MHz = 1294400, /* BBN BitGraph PSG */
XTAL_1_75MHz = 1750000, /* RCA CDP1861 */
+ XTAL_1_7971MHz = 1797100, /* SWTPC 6800 (with MIKBUG) */
XTAL_1_8432MHz = 1843200, /* Bondwell 12/14 */
XTAL_1_9968MHz = 1996800, /* NEC PC-98xx */
XTAL_2MHz = 2000000,
#n94'>94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216
// license:BSD-3-Clause
// copyright-holders:Aaron Giles
/*****************************************************************************

  7474 positive-edge-triggered D-type flip-flop with preset, clear and
       complementary outputs.  There are 2 flip-flops per chips


  Pin layout and functions to access pins:

  clear_w        [1] /1CLR         VCC [14]
  d_w            [2]  1D         /2CLR [13]  clear_w
  clock_w        [3]  1CLK          2D [12]  d_w
  preset_w       [4] /1PR         2CLK [11]  clock_w
  output_r       [5]  1Q          /2PR [10]  preset_w
  output_comp_r  [6] /1Q            2Q [9]   output_r
                 [7]  GND          /2Q [8]   output_comp_r


  Truth table (all logic levels indicate the actual voltage on the line):

        INPUTS    | OUTPUTS
                  |
    PR  CLR CLK D | Q  /Q
    --------------+-------
 1  L   H   X   X | H   L
 2  H   L   X   X | L   H
 3  L   L   X   X | H   H  (Note 1)
 4  H   H  _-   X | D  /D
 5  H   H   L   X | Q0 /Q0
    --------------+-------
    L   = lo (0)
    H   = hi (1)
    X   = any state
    _-  = raising edge
    Q0  = previous state

    Note 1: Non-stable configuration

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

#include "emu.h"
#include "7474.h"



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

// device type definition
const device_type TTL7474 = &device_creator<ttl7474_device>;

//-------------------------------------------------
//  ttl7474_device - constructor
//-------------------------------------------------

ttl7474_device::ttl7474_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
	: device_t(mconfig, TTL7474, "7474 TTL", tag, owner, clock, "7474", __FILE__),
		m_output_func(*this),
		m_comp_output_func(*this)
{
	init();
}

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

void ttl7474_device::device_start()
{
	save_item(NAME(m_clear));
	save_item(NAME(m_preset));
	save_item(NAME(m_clk));
	save_item(NAME(m_d));
	save_item(NAME(m_output));
	save_item(NAME(m_output_comp));
	save_item(NAME(m_last_clock));
	save_item(NAME(m_last_output));
	save_item(NAME(m_last_output_comp));

	m_output_func.resolve_safe();
	m_comp_output_func.resolve_safe();
}


//-------------------------------------------------
//  device_reset - device-specific reset
//-------------------------------------------------

void ttl7474_device::device_reset()
{
	init();
}


//-------------------------------------------------
//  update - update internal state
//-------------------------------------------------

void ttl7474_device::update()
{
	if (!m_preset && m_clear)           // line 1 in truth table
	{
		m_output    = 1;
		m_output_comp = 0;
	}
	else if (m_preset && !m_clear)      // line 2 in truth table
	{
		m_output    = 0;
		m_output_comp = 1;
	}
	else if (!m_preset && !m_clear)     // line 3 in truth table
	{
		m_output    = 1;
		m_output_comp = 1;
	}
	else if (!m_last_clock && m_clk)    // line 4 in truth table
	{
		m_output    =  m_d;
		m_output_comp = !m_d;
	}

	m_last_clock = m_clk;


	// call callback if any of the outputs changed
	if (m_output != m_last_output)
	{
		m_last_output = m_output;
		m_output_func(m_output);
	}
	// call callback if any of the outputs changed
	if (m_output_comp != m_last_output_comp)
	{
		m_last_output_comp = m_output_comp;
		m_comp_output_func(m_output_comp);
	}
}


//-------------------------------------------------
//  clear_w - set the clear line state
//-------------------------------------------------

WRITE_LINE_MEMBER( ttl7474_device::clear_w )
{
	m_clear = state & 1;
	update();
}


//-------------------------------------------------
//  clear_w - set the clear line state
//-------------------------------------------------

WRITE_LINE_MEMBER( ttl7474_device::preset_w )
{
	m_preset = state & 1;
	update();
}


//-------------------------------------------------
//  clock_w - set the clock line state
//-------------------------------------------------

WRITE_LINE_MEMBER( ttl7474_device::clock_w )
{
	m_clk = state & 1;
	update();
}


//-------------------------------------------------
//  d_w - set the d line state
//-------------------------------------------------

WRITE_LINE_MEMBER( ttl7474_device::d_w )
{
	m_d = state & 1;
	update();
}


//-------------------------------------------------
//  output_r - get the output line state
//-------------------------------------------------

READ_LINE_MEMBER( ttl7474_device::output_r )
{
	return m_output;
}


//-----------------------------------------------------
//  output_comp_r - get the output-compare line state
//-----------------------------------------------------

READ_LINE_MEMBER( ttl7474_device::output_comp_r )
{
	return m_output_comp;
}

void ttl7474_device::init()
{
	m_clear = 1;
	m_preset = 1;
	m_clk = 1;
	m_d = 1;

	m_output = -1;
	m_last_clock = 1;
	m_last_output = -1;
	m_last_output_comp = -1;
}