From ad5d4ba44184af2759443a6755457536ebd5f0d9 Mon Sep 17 00:00:00 2001
From: Fabio Priuli <etabeta78@users.noreply.github.com>
Date: Sat, 6 Sep 2014 10:30:13 +0000
Subject: [PATCH] (MESS) a7800: more accurate POKEY accesses make Beef Drop
 happier. nw.

---
 src/emu/bus/a7800/rom.c | 30 +++++++++++++++++++++++++++---
 src/emu/bus/a7800/rom.h |  2 ++
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/src/emu/bus/a7800/rom.c b/src/emu/bus/a7800/rom.c
index ca05895bebe..0796756fea3 100644
--- a/src/emu/bus/a7800/rom.c
+++ b/src/emu/bus/a7800/rom.c
@@ -7,8 +7,11 @@
  - pokey or not
  - 9 banks or not
  etc...
- But we might merge many of these if they become too many (e.g. could there be banked 32L RAM also
- in a 9banks cart or in a cart with no bankswitch?)
+ But we might merge many of these if they become too many
+ 
+ TODO:
+ - Are POKEY regs readable somewhere in SG 144K + POKEY homebrew? How do they detect
+   the POKEY otherwise?!?
 
 ***********************************************************************************************************/
 
@@ -182,6 +185,17 @@ READ8_MEMBER(a78_rom_device::read_40xx)
  
  -------------------------------------------------*/
 
+READ8_MEMBER(a78_rom_pokey_device::read_40xx)
+{
+	if (offset < 0x4000)
+		return m_pokey->read(space, offset & 0x0f);
+
+	if (offset + 0x4000 < m_base_rom)
+		return 0xff;
+	else
+		return m_rom[offset + 0x4000 - m_base_rom];
+}
+
 WRITE8_MEMBER(a78_rom_pokey_device::write_40xx)
 {
 	if (offset < 0x4000)
@@ -233,10 +247,20 @@ WRITE8_MEMBER(a78_rom_sg_device::write_40xx)
  Carts with SuperGame bankswitch + POKEY chip
  As above + Pokey chip access
  
- GAMES: Commando
+ GAMES: Commando and Barnyard Blaster
  
  -------------------------------------------------*/
 
+READ8_MEMBER(a78_rom_sg_pokey_device::read_40xx)
+{
+	if (offset < 0x4000)
+		return m_pokey->read(space, offset & 0x0f);
+	else if (offset < 0x8000)
+		return m_rom[(offset & 0x3fff) + (m_bank * 0x4000)];
+	else
+		return m_rom[(offset & 0x3fff) + (m_bank_mask * 0x4000)];	// last bank
+}
+
 WRITE8_MEMBER(a78_rom_sg_pokey_device::write_40xx)
 {
 	if (offset < 0x4000)
diff --git a/src/emu/bus/a7800/rom.h b/src/emu/bus/a7800/rom.h
index 335c8aba1d9..0a67d6d0de2 100644
--- a/src/emu/bus/a7800/rom.h
+++ b/src/emu/bus/a7800/rom.h
@@ -36,6 +36,7 @@ public:
 	virtual machine_config_constructor device_mconfig_additions() const;
 	
 	// reading and writing
+	virtual DECLARE_READ8_MEMBER(read_40xx);
 	virtual DECLARE_WRITE8_MEMBER(write_40xx);
 	
 protected:
@@ -77,6 +78,7 @@ public:
 	virtual machine_config_constructor device_mconfig_additions() const;
 	
 	// reading and writing
+	virtual DECLARE_READ8_MEMBER(read_40xx);
 	virtual DECLARE_WRITE8_MEMBER(write_40xx);
 	
 protected: