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+// 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;
+}