gen_latch: Invert logic (latch_read -> latch_written).

Also fixes initial callback after start.

src/devices/machine/gen_latch.cpp

@@ -26,7 +26,7 @@ const device_type GENERIC_LATCH_16 = &device_creator<generic_latch_16_device>;
 
 generic_latch_base_device::generic_latch_base_device(const machine_config &mconfig, device_type type, const char *name, const char *tag, device_t *owner, u32 clock, const char *shortname, const char *source) :
 	device_t(mconfig, type, name, tag, owner, clock, shortname, source),
-	m_latch_read(false),
+	m_latch_written(false),
 	m_data_pending_cb(*this)
 {
 }
@@ -38,7 +38,16 @@ generic_latch_base_device::generic_latch_base_device(const machine_config &mconf
 void generic_latch_base_device::device_start()
 {
 	m_data_pending_cb.resolve_safe();
-	save_item(NAME(m_latch_read));
+	save_item(NAME(m_latch_written));
+}
+
+//-------------------------------------------------
+//  device_reset - device-specific reset
+//-------------------------------------------------
+
+void generic_latch_base_device::device_reset()
+{
+	m_latch_written = false;
 }
 
 //-------------------------------------------------
@@ -48,20 +57,20 @@ void generic_latch_base_device::device_start()
 
 READ_LINE_MEMBER(generic_latch_base_device::pending_r)
 {
-	return !m_latch_read;
+	return m_latch_written ? 1 : 0;
 }
 
 //-------------------------------------------------
-//  set_latch_read - helper to signal that latch
+//  set_latch_written - helper to signal that latch
-//  has been read or is waiting to be read
+//  has been written or has been read
 //-------------------------------------------------
 
-void generic_latch_base_device::set_latch_read(bool latch_read)
+void generic_latch_base_device::set_latch_written(bool latch_written)
 {
-	if (m_latch_read != latch_read)
+	if (m_latch_written != latch_written)
 	{
-		m_latch_read = latch_read;
+		m_latch_written = latch_written;
-		m_data_pending_cb(!latch_read);
+		m_data_pending_cb(latch_written ? 1 : 0);
 	}
 }
 
@@ -77,7 +86,7 @@ generic_latch_8_device::generic_latch_8_device(const machine_config &mconfig, co
 
 READ8_MEMBER( generic_latch_8_device::read )
 {
-	set_latch_read(true);
+	set_latch_written(false);
 	return m_latched_value;
 }
 
@@ -115,13 +124,13 @@ void generic_latch_8_device::sync_callback(void *ptr, s32 param)
 {
 	u8 value = param;
 
-	// if the latch hasn't been read and the value is changed, log a warning
+	// if the latch has been written and the value is changed, log a warning
-	if (!is_latch_read() && m_latched_value != value)
+	if (is_latch_written() && m_latched_value != value)
 		logerror("Warning: latch written before being read. Previous: %02x, new: %02x\n", m_latched_value, value);
 
 	// store the new value and mark it not read
 	m_latched_value = value;
-	set_latch_read(false);
+	set_latch_written(true);
 }
 
 //-------------------------------------------------
@@ -147,7 +156,7 @@ generic_latch_16_device::generic_latch_16_device(const machine_config &mconfig,
 
 READ16_MEMBER( generic_latch_16_device::read )
 {
-	set_latch_read(true);
+	set_latch_written(false);
 	return m_latched_value;
 }
 
@@ -185,13 +194,13 @@ void generic_latch_16_device::sync_callback(void *ptr, s32 param)
 {
 	u16 value = param;
 
-	// if the latch hasn't been read and the value is changed, log a warning
+	// if the latch has been written and the value is changed, log a warning
-	if (!is_latch_read() && m_latched_value != value)
+	if (is_latch_written() && m_latched_value != value)
 		logerror("Warning: latch written before being read. Previous: %02x, new: %02x\n", m_latched_value, value);
 
 	// store the new value and mark it not read
 	m_latched_value = value;
-	set_latch_read(false);
+	set_latch_written(true);
 }
 
 //-------------------------------------------------

src/devices/machine/gen_latch.h

@@ -46,12 +46,13 @@ public:
 
 protected:
 	virtual void device_start() override;
+	virtual void device_reset() override;
 
-	bool is_latch_read() const { return m_latch_read; }
+	bool is_latch_written() const { return m_latch_written; }
-	void set_latch_read(bool latch_read);
+	void set_latch_written(bool latch_written);
 
 private:
-	bool                    m_latch_read;
+	bool                    m_latch_written;
 	devcb_write_line        m_data_pending_cb;				
 };