// 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 - 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; }