// 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;
}
}
}
}