apple2: simplify LC handling even further (nw)

src/devices/bus/a2bus/ramcard16k.cpp

@@ -31,13 +31,13 @@ const device_type A2BUS_RAMCARD16K = device_creator<a2bus_ramcard_device>;
 
 a2bus_ramcard_device::a2bus_ramcard_device(const machine_config &mconfig, device_type type, const char *name, const char *tag, device_t *owner, uint32_t clock, const char *shortname, const char *source) :
 	device_t(mconfig, type, name, tag, owner, clock, shortname, source),
-	device_a2bus_card_interface(mconfig, *this), m_inh_state(0), m_last_offset(0), m_last_access(0), m_dxxx_bank(0)
+	device_a2bus_card_interface(mconfig, *this), m_inh_state(0), m_prewrite(false), m_dxxx_bank(0)
 {
 }
 
 a2bus_ramcard_device::a2bus_ramcard_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
 	device_t(mconfig, A2BUS_RAMCARD16K, "Apple II 16K Language Card", tag, owner, clock, "a2ram16k", __FILE__),
-	device_a2bus_card_interface(mconfig, *this), m_inh_state(0), m_last_offset(0), m_last_access(0), m_dxxx_bank(0)
+	device_a2bus_card_interface(mconfig, *this), m_inh_state(0), m_prewrite(false), m_dxxx_bank(0)
 {
 }
 
@@ -55,51 +55,63 @@ void a2bus_ramcard_device::device_start()
 	save_item(NAME(m_inh_state));
 	save_item(NAME(m_ram));
 	save_item(NAME(m_dxxx_bank));
-	save_item(NAME(m_last_offset));
+	save_item(NAME(m_prewrite));
-	save_item(NAME(m_last_access));
 }
 
 void a2bus_ramcard_device::device_reset()
 {
 	m_inh_state = INH_WRITE;
 	m_dxxx_bank = 0;
-	m_last_offset = -1;
+	m_prewrite = false;
-	m_last_access = 0;
 }
 
-void a2bus_ramcard_device::do_io(int offset, int access)
+void a2bus_ramcard_device::do_io(int offset, bool writing)
 {
 	int old_inh_state = m_inh_state;
 
-	m_inh_state = INH_NONE;
+	//any even access disables pre-write and writing
+	if ((offset & 1) == 0)
+	{
+		m_prewrite = false;
+		m_inh_state &= ~INH_WRITE;
+	}
+
+	//any write disables pre-write
+	//has no effect on write-enable if writing was enabled already
+	if (writing == true)
+	{
+		m_prewrite = false;
+	}
+	//first odd read enables pre-write, second one enables writing
+	else if ((offset & 1) == 1)
+	{
+		if (m_prewrite == false)
+		{
+			m_prewrite = true;
+		}
+		else
+		{
+			m_inh_state |= INH_WRITE;
+		}
+	}
 
 	switch (offset & 3)
 	{
 		case 0:
+		case 3:
 		{
-			m_inh_state = INH_READ;
+			m_inh_state |= INH_READ;
 			break;
 		}
 
-		case 3:
-		{
-			m_inh_state = INH_READ;
-		} //fall through
-
 		case 1:
+		case 2:
 		{
-			//if accessed twice, then write-enable
+			m_inh_state &= ~INH_READ;
-			if (((m_last_offset & 1) == 1) && (access == m_last_access))
-			{
-				m_inh_state |= INH_WRITE;
-			}
-
 			break;
 		}
 	}
 
-	m_last_offset = offset;
-	m_last_access = access;
 	m_dxxx_bank = 0;
 
 	if (!(offset & 8))
@@ -127,7 +139,7 @@ void a2bus_ramcard_device::do_io(int offset, int access)
 
 uint8_t a2bus_ramcard_device::read_c0nx(address_space &space, uint8_t offset)
 {
-	do_io(offset & 0xf, 0);
+	do_io(offset & 0xf, false);
 	return 0xff;
 }
 
@@ -138,7 +150,7 @@ uint8_t a2bus_ramcard_device::read_c0nx(address_space &space, uint8_t offset)
 
 void a2bus_ramcard_device::write_c0nx(address_space &space, uint8_t offset, uint8_t data)
 {
-	do_io(offset & 0xf, 1);
+	do_io(offset & 0xf, true);
 }
 
 uint8_t a2bus_ramcard_device::read_inh_rom(address_space &space, uint16_t offset)

src/devices/bus/a2bus/ramcard16k.h

@@ -40,11 +40,10 @@ protected:
 	virtual int inh_type() override;
 
 private:
-	void do_io(int offset, int access);
+	void do_io(int offset, bool writing);
 
 	int m_inh_state;
-	int m_last_offset;
+	bool m_prewrite;
-	int m_last_access;
 	int m_dxxx_bank;
 	uint8_t m_ram[16*1024];
 };

src/mame/drivers/apple2e.cpp

@@ -369,8 +369,7 @@ private:
 	bool m_slotc3rom;
 	bool m_altzp;
 	bool m_ramrd, m_ramwrt;
-	bool m_lcram, m_lcram2, m_lcwriteenable;
+	bool m_lcram, m_lcram2, m_lcprewrite, m_lcwriteenable;
-	int m_last_offset, m_last_access;
 	bool m_ioudis;
 	bool m_romswitch;
 	bool m_mockingboard4c;
@@ -402,7 +401,7 @@ private:
 	void do_io(address_space &space, int offset, bool is_iic);
 	uint8_t read_floatingbus();
 	void update_slotrom_banks();
-	void lc_update(int offset, int access);
+	void lc_update(int offset, bool writing);
 	uint8_t read_slot_rom(address_space &space, int slotbias, int offset);
 	void write_slot_rom(address_space &space, int slotbias, int offset, uint8_t data);
 	uint8_t read_int_rom(address_space &space, int slotbias, int offset);
@@ -702,9 +701,8 @@ void apple2e_state::machine_start()
 	save_item(NAME(m_exp_addrmask));
 	save_item(NAME(m_lcram));
 	save_item(NAME(m_lcram2));
+	save_item(NAME(m_lcprewrite));
 	save_item(NAME(m_lcwriteenable));
-	save_item(NAME(m_last_offset));
-	save_item(NAME(m_last_access));
 	save_item(NAME(m_mockingboard4c));
 	save_item(NAME(m_intc8rom));
 }
@@ -760,9 +758,8 @@ void apple2e_state::machine_reset()
 	// LC default state: read ROM, write enabled, Dxxx bank 2
 	m_lcram = false;
 	m_lcram2 = true;
+	m_lcprewrite = false;
 	m_lcwriteenable = true;
-	m_last_offset = -1;
-	m_last_access = 0;
 
 	m_exp_bankhior = 0xf0;
 
@@ -1012,40 +1009,53 @@ void apple2e_state::update_slotrom_banks()
 	}
 }
 
-void apple2e_state::lc_update(int offset, int access)
+void apple2e_state::lc_update(int offset, bool writing)
 {
 	bool old_lcram = m_lcram;
 
-	m_lcram = false;
+	//any even access disables pre-write and writing
-	m_lcwriteenable = false;
+	if ((offset & 1) == 0)
+	{
+		m_lcprewrite = false;
+		m_lcwriteenable = false;
+	}
+
+	//any write disables pre-write
+	//has no effect on write-enable if writing was enabled already
+	if (writing == true)
+	{
+		m_lcprewrite = false;
+	}
+	//first odd read enables pre-write, second one enables writing
+	else if ((offset & 1) == 1)
+	{
+		if (m_lcprewrite == false)
+		{
+			m_lcprewrite = true;
+		}
+		else
+		{
+			m_lcwriteenable = true;
+		}
+	}
 
 	switch (offset & 3)
 	{
 		case 0:
+		case 3:
 		{
 			m_lcram = true;
 			break;
 		}
 
-		case 3:
-		{
-			m_lcram = true;
-		} //fall through
-
 		case 1:
+		case 2:
 		{
-			//if accessed twice, then write-enable
+			m_lcram = false;
-			if (((m_last_offset & 1) == 1) && (access == m_last_access))
-			{
-				m_lcwriteenable = true;
-			}
-
 			break;
 		}
 	}
 
-	m_last_offset = offset;
-	m_last_access = access;
 	m_lcram2 = false;
 
 	if (!(offset & 8))
@@ -1865,7 +1875,7 @@ READ8_MEMBER(apple2e_state::c080_r)
 
 		if (slot == 0)
 		{
-			lc_update(offset & 0xf, 0);
+			lc_update(offset & 0xf, false);
 		}
 		else
 		{
@@ -1888,7 +1898,7 @@ WRITE8_MEMBER(apple2e_state::c080_w)
 
 	if (slot == 0)
 	{
-		lc_update(offset & 0xf, 1);
+		lc_update(offset & 0xf, true);
 	}
 	else
 	{