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-rw-r--r--src/devices/machine/mm74c922.cpp190
1 files changed, 190 insertions, 0 deletions
diff --git a/src/devices/machine/mm74c922.cpp b/src/devices/machine/mm74c922.cpp
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+++ b/src/devices/machine/mm74c922.cpp
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+// license:BSD-3-Clause
+// copyright-holders:Curt Coder
+/**********************************************************************
+
+ MM74C922/MM74C923 16/20-Key Encoder emulation
+
+**********************************************************************/
+
+#include "mm74c922.h"
+
+
+
+//**************************************************************************
+// MACROS / CONSTANTS
+//**************************************************************************
+
+#define LOG 1
+
+
+
+//**************************************************************************
+// DEVICE DEFINITIONS
+//**************************************************************************
+
+const device_type MM74C922 = &device_creator<mm74c922_device>;
+const device_type MM74C923 = &device_creator<mm74c922_device>;
+
+
+
+
+//**************************************************************************
+// LIVE DEVICE
+//**************************************************************************
+
+//-------------------------------------------------
+// mm74c922_device - constructor
+//-------------------------------------------------
+
+mm74c922_device::mm74c922_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock) :
+ device_t(mconfig, MM74C922, "MM74C922", tag, owner, clock, "mm74c922", __FILE__),
+ 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_max_y(5), // TODO 4 for 74C922, 5 for 74C923
+ m_inhibit(0),
+ m_x(0),
+ m_y(0),
+ m_da(0),
+ m_next_da(0)
+{
+}
+
+
+//-------------------------------------------------
+// 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 mm74c922_device::read()
+{
+ if (LOG) logerror("MM74C922 '%s' Data Read: %02x\n", tag(), 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;
+
+ if (LOG) logerror("MM74C922 '%s' Data Available: %u\n", tag(), 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 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
+
+ if (LOG) logerror("MM74C922 '%s' Key Released\n", tag());
+ }
+ }
+ 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;
+
+ if (LOG) logerror("MM74C922 '%s' Key Depressed: X %u Y %u = %02x\n", tag(), m_x, y, m_data);
+ return;
+ }
+ }
+ }
+}