// license:BSD-3-Clause // copyright-holders:Ryan Holtz /***************************************************************************** 7400 Quad 2-Input NAND Gate *****************************************************************************/ #include "emu.h" #include "7400.h" const device_type TTL7400 = &device_creator; ttl7400_device::ttl7400_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) : device_t(mconfig, TTL7400, "7400 Quad 2-Input NAND Gate", tag, owner, clock, "7400", __FILE__) , m_y1_func(*this) , m_y2_func(*this) , m_y3_func(*this) , m_y4_func(*this) , m_a(0) , m_b(0) , m_y(0) { } void ttl7400_device::device_start() { init(); save_item(NAME(m_a)); save_item(NAME(m_b)); save_item(NAME(m_y)); m_y1_func.resolve_safe(); m_y2_func.resolve_safe(); m_y3_func.resolve_safe(); m_y4_func.resolve_safe(); } void ttl7400_device::device_reset() { init(); } void ttl7400_device::init() { m_a = 0; m_b = 0; m_y = 0; } void ttl7400_device::update() { uint8_t last_y = m_y; m_y = (m_a & m_b) & 0xf; if (m_y != last_y) { for (int bit = 0; bit < 4; bit++) { if (BIT(m_y, bit) == BIT(last_y, bit)) continue; switch(bit) { case 0: m_y1_func(BIT(m_y, bit)); break; case 1: m_y2_func(BIT(m_y, bit)); break; case 2: m_y3_func(BIT(m_y, bit)); break; case 3: m_y4_func(BIT(m_y, bit)); break; } } } } void ttl7400_device::a_w(uint8_t line, uint8_t state) { uint8_t old_a = m_a; m_a &= ~(1 << line); m_a |= (state << line); if (old_a != m_a) update(); } void ttl7400_device::b_w(uint8_t line, uint8_t state) { uint8_t old_b = m_b; m_b &= ~(1 << line); m_b |= (state << line); if (old_b != m_b) update(); } uint8_t ttl7400_device::y_r(uint8_t line) { return (m_y >> line) & 1; } WRITE_LINE_MEMBER( ttl7400_device::a1_w ) { a_w(0, state); } WRITE_LINE_MEMBER( ttl7400_device::a2_w ) { a_w(1, state); } WRITE_LINE_MEMBER( ttl7400_device::a3_w ) { a_w(2, state); } WRITE_LINE_MEMBER( ttl7400_device::a4_w ) { a_w(3, state); } WRITE_LINE_MEMBER( ttl7400_device::b1_w ) { b_w(0, state); } WRITE_LINE_MEMBER( ttl7400_device::b2_w ) { b_w(1, state); } WRITE_LINE_MEMBER( ttl7400_device::b3_w ) { b_w(2, state); } WRITE_LINE_MEMBER( ttl7400_device::b4_w ) { b_w(3, state); } READ_LINE_MEMBER( ttl7400_device::y1_r ) { return y_r(0); } READ_LINE_MEMBER( ttl7400_device::y2_r ) { return y_r(1); } READ_LINE_MEMBER( ttl7400_device::y3_r ) { return y_r(2); } READ_LINE_MEMBER( ttl7400_device::y4_r ) { return y_r(3); }