mm74c922: data output pins are clocked the same time as DA pin

src/devices/machine/mm74c922.cpp

@@ -34,15 +34,15 @@ DEFINE_DEVICE_TYPE(MM74C923, mm74c923_device, "mm74c923", "MM74C923 20-Key Encod
 
 mm74c922_device::mm74c922_device(const machine_config &mconfig, device_type type, const char *tag, device_t *owner, uint32_t clock, int max_y) :
 	device_t(mconfig, type, tag, owner, clock),
-	m_write_da(*this),
-	m_read_x(*this),
+	m_write_da(*this), m_read_x(*this),
 	m_cap_osc(0), m_cap_debounce(0),
 	m_max_y(max_y),
 	m_inhibit(false),
 	m_x(0),
-	m_y(0), m_data(0),
-	m_da(false),
-	m_next_da(false), m_scan_timer(nullptr)
+	m_y(0),
+	m_data(0), m_next_data(0),
+	m_da(false), m_next_da(false),
+	m_scan_timer(nullptr)
 {
 }
 
@@ -79,6 +79,7 @@ void mm74c922_device::device_start()
 	save_item(NAME(m_x));
 	save_item(NAME(m_y));
 	save_item(NAME(m_data));
+	save_item(NAME(m_next_data));
 	save_item(NAME(m_da));
 	save_item(NAME(m_next_da));
 }
@@ -123,6 +124,12 @@ void mm74c922_device::change_output_lines()
 		// active high output
 		m_write_da(m_da ? 1 : 0);
 	}
+
+	// clock data latches
+	if (m_next_data != m_data)
+	{
+		m_data = m_next_data;
+	}
 }
 
 
@@ -156,7 +163,7 @@ void mm74c922_device::detect_keypress()
 			// key released
 			m_inhibit = false;
 			m_next_da = false;
-			m_data = 0xff; // high-Z
+			m_next_data = (1 << m_max_y) - 1; // high-Z
 
 			LOG("MM74C922 Key Released\n");
 		}
@@ -172,10 +179,9 @@ void mm74c922_device::detect_keypress()
 				m_next_da = true;
 				m_y = y;
 
-				m_data = (y << 2) | m_x;
+				m_next_data = (y << 2) | m_x;
 
-				LOG("MM74C922 Key Depressed: X %u Y %u = %02x\n", m_x, y, m_data);
-				return;
+				LOG("MM74C922 Key Depressed: X %u Y %u = %02x\n", m_x, y, m_next_data);
 			}
 		}
 	}

src/devices/machine/mm74c922.h

@@ -86,6 +86,7 @@ class mm74c922_device :  public device_t
 	int m_y;                    // latched row
 
 	uint8_t m_data;             // data latch
+	uint8_t m_next_data;        // next value of data latch
 
 	bool m_da;                  // data available flag
 	bool m_next_da;             // next value of data available flag

src/mame/drivers/saitek_intchess.cpp

@@ -18,7 +18,8 @@ Hardware notes:
 - 4-digit 7seg display
 
 TODO:
-- remove nmistate workaround when 6502 NMI is fixed
+- 6502 CPU core NMI isn't working properly at the moment, it acts like a hold_line,
+  m_nmistate can be removed once that is fixed
 - colors are estimated from photos (black and white are obvious, but the green
   and cyan are not standard 0x00ff00 / 0x00ffff)
 - video timing is unknown, sprite offsets are estimated from photos
@@ -100,13 +101,15 @@ class intchess_state : public driver_device
 
 	u8 m_select = 0;
 	u8 m_7seg_data = 0;
+	bool m_nmistate = false;
 };
 
 void intchess_state::machine_start()
 {
 	// register for savestates
 	save_item(NAME(m_select));
 	save_item(NAME(m_7seg_data));
+	save_item(NAME(m_nmistate));
 }
 
 INPUT_CHANGED_MEMBER(intchess_state::reset_button)
@@ -205,13 +208,12 @@ u8 intchess_state::control_r()
 TIMER_DEVICE_CALLBACK_MEMBER(intchess_state::cass_input)
 {
 	// cassette input is tied to NMI
-	static bool nmistate = false;
 	bool state = ((m_cass->get_state() & CASSETTE_MASK_UISTATE) == CASSETTE_PLAY) && (m_cass->input() < -0.04);
 
-	if (state != nmistate)
+	if (state != m_nmistate)
 	{
 		m_maincpu->set_input_line(INPUT_LINE_NMI, state ? ASSERT_LINE : CLEAR_LINE);
-		nmistate = state;
+		m_nmistate = state;
 	}
 }