// license:BSD-3-Clause // copyright-holders:Curt Coder /********************************************************************** MM74C922/MM74C923 16/20-Key Encoder emulation **********************************************************************/ #include "emu.h" #include "mm74c922.h" //#define VERBOSE 1 #include "logmacro.h" //************************************************************************** // DEVICE DEFINITIONS //************************************************************************** DEFINE_DEVICE_TYPE(MM74C922, mm74c922_device, "mm74c922", "MM74C923 16/20-Key Encoder") decltype(MM74C922) MM74C923 = MM74C922; //************************************************************************** // LIVE DEVICE //************************************************************************** //------------------------------------------------- // mm74c922_device - constructor //------------------------------------------------- mm74c922_device::mm74c922_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) : device_t(mconfig, MM74C922, tag, owner, clock), m_write_da(*this), m_read_x1(*this), m_read_x2(*this), m_read_x3(*this), m_read_x4(*this), m_read_x5(*this), m_cap_osc(0), m_cap_debounce(0), m_max_y(5), // TODO 4 for 74C922, 5 for 74C923 m_inhibit(0), m_x(0), m_y(0), m_data(0), m_da(0), m_next_da(0), m_scan_timer(nullptr) { } //------------------------------------------------- // device_start - device-specific startup //------------------------------------------------- void mm74c922_device::device_start() { // resolve callbacks m_write_da.resolve_safe(); m_read_x1.resolve_safe(0); m_read_x2.resolve_safe(0); m_read_x3.resolve_safe(0); m_read_x4.resolve_safe(0); m_read_x5.resolve_safe(0); // set initial values change_output_lines(); // allocate timers m_scan_timer = timer_alloc(); m_scan_timer->adjust(attotime::zero, 0, attotime::from_hz(50)); // register for state saving save_item(NAME(m_inhibit)); save_item(NAME(m_x)); save_item(NAME(m_y)); save_item(NAME(m_data)); save_item(NAME(m_da)); save_item(NAME(m_next_da)); } //------------------------------------------------- // device_timer - handler timer events //------------------------------------------------- void mm74c922_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr) { change_output_lines(); clock_scan_counters(); detect_keypress(); } //------------------------------------------------- // read - //------------------------------------------------- uint8_t mm74c922_device::read() { LOG("MM74C922 Data Read: %02x\n", m_data); return m_data; } //------------------------------------------------- // change_output_lines - //------------------------------------------------- void mm74c922_device::change_output_lines() { if (m_next_da != m_da) { m_da = m_next_da; LOG("MM74C922 Data Available: %u\n", m_da); m_write_da(m_da); } } //------------------------------------------------- // clock_scan_counters - //------------------------------------------------- void mm74c922_device::clock_scan_counters() { if (!m_inhibit) { m_x++; m_x &= 0x03; } } //------------------------------------------------- // detect_keypress - //------------------------------------------------- void mm74c922_device::detect_keypress() { uint8_t data = 0xff; switch (m_x) { case 0: data = m_read_x1(0); break; case 1: data = m_read_x2(0); break; case 2: data = m_read_x3(0); break; case 3: data = m_read_x4(0); break; case 4: data = m_read_x5(0); break; } if (m_inhibit) { if (BIT(data, m_y)) { // key released m_inhibit = 0; m_next_da = 0; m_data = 0xff; // high-Z LOG("MM74C922 Key Released\n"); } } else { for (int y = 0; y < m_max_y; y++) { if (!BIT(data, y)) { // key depressed m_inhibit = 1; m_next_da = 1; m_y = y; m_data = (y << 2) | m_x; LOG("MM74C922 Key Depressed: X %u Y %u = %02x\n", m_x, y, m_data); return; } } } }