From 1aa7194558671113ed8f9592b6569dc68c696c7b Mon Sep 17 00:00:00 2001
From: Fabio Priuli <etabeta78@users.noreply.github.com>
Date: Fri, 7 Feb 2014 13:30:33 +0000
Subject: [PATCH] (MESS) nes_mmc5: further cleanups (this time for NT-RAM
 handling). no visible improvements, but it bothered me that we were saving as
 NVRAM the external RAM, while it was volatile in real carts. nw.

---
 src/mess/machine/nes_mmc5.c | 74 +++++++++++++++++++++++++------------
 src/mess/machine/nes_mmc5.h |  1 +
 src/mess/machine/nes_slot.c |  8 ++--
 3 files changed, 54 insertions(+), 29 deletions(-)

diff --git a/src/mess/machine/nes_mmc5.c b/src/mess/machine/nes_mmc5.c
index b20f004056d..6e9d4da0873 100644
--- a/src/mess/machine/nes_mmc5.c
+++ b/src/mess/machine/nes_mmc5.c
@@ -79,9 +79,6 @@ void nes_exrom_device::device_start()
 
 	m_exram = auto_alloc_array_clear(machine(), UINT8, 0x400);
 	save_pointer(NAME(m_exram), 0x400);
-
-	m_mapper_sram_size = 0x400;
-	m_mapper_sram = m_exram;
 }
 
 void nes_exrom_device::pcb_reset()
@@ -121,22 +118,6 @@ void nes_exrom_device::pcb_reset()
 }
 
 
-READ8_MEMBER(nes_exrom_device::nt_r)
-{
-	int page = ((offset & 0xc00) >> 10);
-
-	if (m_nt_src[page] == MMC5FILL)
-	{
-		if ((offset & 0x3ff) >= 0x3c0)
-			return m_floodattr;
-
-		return m_floodtile;
-	}
-	return m_nt_access[page][offset & 0x3ff];
-}
-
-
-
 /*-------------------------------------------------
  mapper specific handlers
  -------------------------------------------------*/
@@ -348,16 +329,16 @@ void nes_exrom_device::set_mirror(int page, int src)
 {
 	switch (src)
 	{
-		case 0: /* CIRAM0 */
+		case 0:
 			set_nt_page(page, CIRAM, 0, 1);
 			break;
-		case 1: /* CIRAM1 */
+		case 1:
 			set_nt_page(page, CIRAM, 1, 1);
 			break;
-		case 2: /* ExRAM */
-			set_nt_page(page, EXRAM, 0, 1);  // actually only works during rendering.
+		case 2:
+			set_nt_page(page, EXRAM, 0, 1);
 			break;
-		case 3: /* Fill Registers */
+		case 3:
 			set_nt_page(page, MMC5FILL, 0, 0);
 			break;
 		default:
@@ -366,6 +347,51 @@ void nes_exrom_device::set_mirror(int page, int src)
 	}
 }
 
+
+READ8_MEMBER(nes_exrom_device::nt_r)
+{
+	int page = ((offset & 0xc00) >> 10);
+
+	switch (m_nt_src[page])
+	{
+		case MMC5FILL:
+			if ((offset & 0x3ff) >= 0x3c0)
+				return m_floodattr;			
+			return m_floodtile;
+
+		case EXRAM:
+			if (!BIT(m_exram_control, 1))
+				return m_exram[offset & 0x3ff];
+			else
+				return 0x00;
+
+		case CIRAM:
+		default:
+			return m_nt_access[page][offset & 0x3ff];
+	}
+}
+
+WRITE8_MEMBER(nes_exrom_device::nt_w)
+{
+	int page = ((offset & 0xc00) >> 10);	
+	
+	if (!m_nt_writable[page])
+		return;
+	
+	switch (m_nt_src[page])
+	{
+		case EXRAM:
+			m_exram[offset & 0x3ff] = data;
+			break;
+			
+		case CIRAM:
+		default:
+			m_nt_access[page][offset & 0x3ff] = data;
+			break;
+	}
+}
+
+
 READ8_MEMBER(nes_exrom_device::read_l)
 {
 	int value;
diff --git a/src/mess/machine/nes_mmc5.h b/src/mess/machine/nes_mmc5.h
index e8077fd71c6..bdaf359ae32 100644
--- a/src/mess/machine/nes_mmc5.h
+++ b/src/mess/machine/nes_mmc5.h
@@ -19,6 +19,7 @@ public:
 	virtual DECLARE_WRITE8_MEMBER(write_l);
 	virtual DECLARE_WRITE8_MEMBER(write_m);
 	virtual DECLARE_READ8_MEMBER(nt_r);
+	virtual DECLARE_WRITE8_MEMBER(nt_w);
 
 	virtual void hblank_irq(int scanline, int vblank, int blanked);
 	virtual void pcb_reset();
diff --git a/src/mess/machine/nes_slot.c b/src/mess/machine/nes_slot.c
index 98f13cecfeb..e96f3cc3d0a 100644
--- a/src/mess/machine/nes_slot.c
+++ b/src/mess/machine/nes_slot.c
@@ -503,15 +503,13 @@ void device_nes_cart_interface::set_nt_page(int page, int source, int bank, int
 		case CART_NTRAM:
 			base_ptr = m_ext_ntram;
 			break;
-		case MMC5FILL:
-			base_ptr = NULL;
-			break;
 		case VROM:
 			bank &= ((m_vrom_chunks << 3) - 1);
 			base_ptr = m_vrom;
 			break;
 		case EXRAM:
-			base_ptr = m_mapper_sram;
+		case MMC5FILL:
+			base_ptr = NULL;
 			break;
 		case CIRAM:
 		default:
@@ -522,7 +520,7 @@ void device_nes_cart_interface::set_nt_page(int page, int source, int bank, int
 	page &= 3; /* mask down to the 4 logical pages */
 	m_nt_src[page] = source;
 
-	if (base_ptr != NULL)
+	if (base_ptr)
 	{
 		m_nt_orig[page] = bank * 0x400;
 		m_nt_access[page] = base_ptr + m_nt_orig[page];