(MESS) nes.c: slightly more refined open bus emulation (still not 100% accurate, but it suffices

to make happy the two games which had issues with previous implementation). nw

src/mess/machine/nes_bootleg.c

@@ -969,7 +969,7 @@ READ8_MEMBER(nes_smb2j_device::read_l)
 	if (offset >= 0x1000)
 		return m_prg[0x10000 + (offset & 0x0fff)];
 
-	return ((offset + 0x4000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 READ8_MEMBER(nes_smb2j_device::read_m)

src/mess/machine/nes_jy.c

@@ -283,7 +283,7 @@ READ8_MEMBER(nes_jy_typea_device::read_l)
 		if ((offset & 3) == 3)
 			return m_latch;
 	}
-	return ((offset + 0x4000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 WRITE8_MEMBER(nes_jy_typea_device::write_l)
@@ -310,7 +310,7 @@ READ8_MEMBER(nes_jy_typea_device::read_m)
 	if (m_reg[0] & 0x80)
 		return m_prg[(m_bank_6000 & m_prg_mask) * 0x2000 + (offset & 0x1fff)];
 
-	return ((offset + 0x6000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 

src/mess/machine/nes_kaiser.c

@@ -476,7 +476,7 @@ READ8_MEMBER(nes_ks7017_device::read_ex)
 		return temp;
 	}
 
-	return ((offset + 0x4000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 /*-------------------------------------------------

src/mess/machine/nes_konami.c

@@ -295,7 +295,7 @@ READ8_MEMBER(nes_konami_vrc2_device::read_m)
 	else if (m_prgram)
 		return m_prgram[offset & (m_prgram_size - 1)];
 	else    // sort of protection? it returns open bus in $7000-$7fff and (open bus & 0xfe) | m_latch in $6000-$6fff
-		return (offset < 0x1000) ? ((((offset + 0x8000) & 0xfe00) >> 8) | (m_latch & 1)) : (((offset + 0x8000) & 0xff00) >> 8);
+		return (offset < 0x1000) ? ((m_open_bus & 0xfe) | (m_latch & 1)) : m_open_bus;
 }
 
 WRITE8_MEMBER(nes_konami_vrc2_device::write_m)
@@ -602,9 +602,7 @@ WRITE8_MEMBER(nes_konami_vrc6_device::write_h)
 				}
 			}
 			else    // saw
-			{
 				m_vrc6snd->write(space, (add_lines>>8) | 0x200, data);
-			}
 			break;
 		case 0x5000:
 		case 0x6000:

src/mess/machine/nes_mmc1.c

@@ -293,7 +293,7 @@ READ8_MEMBER(nes_sxrom_device::read_m)
 			return m_prgram[((bank * 0x2000) + offset) & (m_prgram_size - 1)];
 	}
 
-	return ((offset + 0x6000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 // SOROM has two RAM banks, the first is not battery backed up, the second is.
@@ -324,7 +324,7 @@ READ8_MEMBER(nes_sorom_device::read_m)
 			return m_prgram[offset & (m_prgram_size - 1)];
 	}
 
-	return ((offset + 0x6000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 // MMC1A boards have no wram enable/disable bit
@@ -349,7 +349,7 @@ READ8_MEMBER(nes_sxrom_a_device::read_m)
 	if (m_prgram)
 		return m_prgram[((bank * 0x2000) + offset) & (m_prgram_size - 1)];
 
-	return ((offset + 0x6000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 WRITE8_MEMBER(nes_sorom_a_device::write_m)

src/mess/machine/nes_mmc3.c

@@ -340,7 +340,7 @@ READ8_MEMBER(nes_txrom_device::read_m)
 			return m_prgram[offset & (m_prgram_size - 1)];
 	}
 
-	return ((offset + 0x6000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 
@@ -376,10 +376,10 @@ READ8_MEMBER(nes_hkrom_device::read_m)
 	LOG_MMC(("hkrom read_m, offset: %04x\n", offset));
 
 	if (offset < 0x1000)
-		return 0xff;    // here it should be open bus
+		return m_open_bus;    // open bus
 
 	if (!(m_mmc6_reg & 0xa0))
-		return 0xff;    // here it should be open bus
+		return m_open_bus;    // open bus
 
 	if (BIT(offset, 9) && BIT(m_mmc6_reg, 7))   // access to upper half of 1k when upper read is enabled
 		return m_mmc6_ram[offset & 0x3ff];

src/mess/machine/nes_mmc3_clones.c

@@ -444,10 +444,10 @@ void nes_a9746_device::pcb_reset()
 {
 	m_chr_source = m_vrom_chunks ? CHRROM : CHRRAM;
 
-	mmc3_common_initialize(0x7f, 0xff, 0);
 	m_reg[0] = 0;
 	m_reg[1] = 0;
 	m_reg[2] = 0;
+	mmc3_common_initialize(0x7f, 0xff, 0);
 }
 
 void nes_fk23c_device::device_start()
@@ -1797,7 +1797,7 @@ READ8_MEMBER( nes_sachen_shero_device::read_l )
 	{
 		// DSW read!
 	}
-	return (offset & 0xff00) >> 8;  // open bus
+	return m_open_bus;  // open bus
 }
 
 

src/mess/machine/nes_multigame.c

@@ -1476,7 +1476,7 @@ READ8_MEMBER(nes_bmc_gb63_device::read_h)
 	//  m_dipsetting = ioport("CARTDIPS")->read();
 
 	if (m_latch == 1)
-		return (offset & 0xff00) >> 8;    // open bus
+		return m_open_bus;    // open bus
 	else
 		return hi_access_rom(offset);
 }
@@ -2458,7 +2458,7 @@ READ8_MEMBER(nes_bmc_gold150_device::read_h)
 	LOG_MMC(("bmc_gold150 read_h, offset: %04x\n", offset));
 
 	if (m_latch)    // open bus
-		return (offset & 0xff00) >> 8;
+		return m_open_bus;
 	else
 		return hi_access_rom(offset);
 }
@@ -2511,7 +2511,7 @@ READ8_MEMBER(nes_bmc_ch001_device::read_h)
 	LOG_MMC(("bmc_ch001 read_h, offset: %04x\n", offset));
 
 	if (m_latch && offset < 0x4000) // open bus
-		return (offset & 0xff00) >> 8;
+		return m_open_bus;
 	else
 		return hi_access_rom(offset);
 }

src/mess/machine/nes_namcot.c

@@ -520,7 +520,7 @@ READ8_MEMBER(nes_namcot175_device::read_m)
 	if (m_battery && offset < m_battery_size && m_wram_enable)
 		return m_battery[offset & (m_battery_size - 1)];
 
-	return ((offset + 0x6000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 WRITE8_MEMBER(nes_namcot175_device::write_m)
@@ -602,7 +602,7 @@ READ8_MEMBER(nes_namcot163_device::read_m)
 	if (m_battery && offset < m_battery_size)
 		return m_battery[offset & (m_battery_size - 1)];
 
-	return ((offset + 0x6000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 WRITE8_MEMBER(nes_namcot163_device::write_m)

src/mess/machine/nes_pirate.c

@@ -1384,6 +1384,6 @@ READ8_MEMBER(nes_fujiya_device::read_m)
 	if (offset == 0x7001 || offset == 0x7777)
 		return m_latch | ((offset >> 8) & 0x7f);
 
-	return (offset & 0xff00) >> 8;  // open bus
+	return m_open_bus;  // open bus
 }
 #endif

src/mess/machine/nes_slot.c

@@ -130,6 +130,7 @@ device_nes_cart_interface::device_nes_cart_interface(const machine_config &mconf
 						m_has_trainer(FALSE),
 						m_x1_005_alt_mirroring(FALSE),
 						m_bus_conflict(TRUE),
+						m_open_bus(0),
 						m_prg_chunks(0),
 						m_prg_mask(0xffff),
 						m_chr_source(CHRRAM),
@@ -656,7 +657,7 @@ READ8_MEMBER(device_nes_cart_interface::nt_r)
 
 READ8_MEMBER(device_nes_cart_interface::read_l)
 {
-	return ((offset + 0x4100) & 0xff00) >> 8;   // open bus
+	return m_open_bus;
 }
 
 READ8_MEMBER(device_nes_cart_interface::read_m)
@@ -666,7 +667,7 @@ READ8_MEMBER(device_nes_cart_interface::read_m)
 	if (m_prgram)
 		return m_prgram[offset & (m_prgram_size - 1)];
 
-	return ((offset + 0x6000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;
 }
 
 WRITE8_MEMBER(device_nes_cart_interface::write_l)
@@ -993,7 +994,12 @@ const char * nes_cart_slot_device::get_default_card_software(const machine_confi
 READ8_MEMBER(nes_cart_slot_device::read_l)
 {
 	if (m_cart)
-		return m_cart->read_l(space, offset);
+	{
+		UINT8 val = m_cart->read_l(space, offset);
+		// update open bus
+		m_cart->set_open_bus(((offset + 0x4100) & 0xff00) >> 8);
+		return val;
+	}
 	else
 		return 0xff;
 }
@@ -1001,7 +1007,12 @@ READ8_MEMBER(nes_cart_slot_device::read_l)
 READ8_MEMBER(nes_cart_slot_device::read_m)
 {
 	if (m_cart)
-		return m_cart->read_m(space, offset);
+	{
+		UINT8 val = m_cart->read_m(space, offset);
+		// update open bus
+		m_cart->set_open_bus(((offset + 0x6000) & 0xff00) >> 8);
+		return val;
+	}
 	else
 		return 0xff;
 }
@@ -1009,7 +1020,12 @@ READ8_MEMBER(nes_cart_slot_device::read_m)
 READ8_MEMBER(nes_cart_slot_device::read_h)
 {
 	if (m_cart)
-		return m_cart->read_h(space, offset);
+	{
+		UINT8 val = m_cart->read_h(space, offset);
+		// update open bus
+		m_cart->set_open_bus(((offset + 0x8000) & 0xff00) >> 8);
+		return val;
+	}
 	else
 		return 0xff;
 }
@@ -1017,7 +1033,12 @@ READ8_MEMBER(nes_cart_slot_device::read_h)
 READ8_MEMBER(nes_cart_slot_device::read_ex)
 {
 	if (m_cart)
-		return m_cart->read_ex(space, offset);
+	{
+		UINT8 val = m_cart->read_ex(space, offset);
+		// update open bus
+		m_cart->set_open_bus(((offset + 0x4020) & 0xff00) >> 8);
+		return val;
+	}
 	else
 		return 0xff;
 }
@@ -1030,25 +1051,41 @@ READ8_MEMBER(nes_cart_slot_device::read_ex)
 WRITE8_MEMBER(nes_cart_slot_device::write_l)
 {
 	if (m_cart)
+	{
 		m_cart->write_l(space, offset, data);
+		// update open bus
+		m_cart->set_open_bus(((offset + 0x4100) & 0xff00) >> 8);
+	}
 }
 
 WRITE8_MEMBER(nes_cart_slot_device::write_m)
 {
 	if (m_cart)
+	{
 		m_cart->write_m(space, offset, data);
+		// update open bus
+		m_cart->set_open_bus(((offset + 0x6000) & 0xff00) >> 8);
+	}
 }
 
 WRITE8_MEMBER(nes_cart_slot_device::write_h)
 {
 	if (m_cart)
+	{
 		m_cart->write_h(space, offset, data);
+		// update open bus
+		m_cart->set_open_bus(((offset + 0x8000) & 0xff00) >> 8);
+	}
 }
 
 WRITE8_MEMBER(nes_cart_slot_device::write_ex)
 {
 	if (m_cart)
+	{
 		m_cart->write_ex(space, offset, data);
+		// update open bus
+		m_cart->set_open_bus(((offset + 0x4020) & 0xff00) >> 8);
+	}
 }
 
 

src/mess/machine/nes_slot.h

@@ -192,6 +192,7 @@ public:
 	void set_vrc_lines(int PRG_A, int PRG_B, int CHR) { m_vrc_ls_prg_a = PRG_A; m_vrc_ls_prg_b = PRG_B; m_vrc_ls_chr = CHR; }
 	void set_x1_005_alt(bool val) { m_x1_005_alt_mirroring = val; }
 	void set_bus_conflict(bool val) { m_bus_conflict = val; }
+	void set_open_bus(UINT8 val) { m_open_bus = val; }
 
 	UINT8* get_prg_base() { return m_prg; }
 	UINT8* get_prgram_base() { return m_prgram; }
@@ -252,6 +253,7 @@ protected:
 	bool m_pcb_ctrl_mirror, m_four_screen_vram, m_has_trainer;
 	bool m_x1_005_alt_mirroring;    // temp hack for two kind of mirroring in Taito X1-005 boards (to be replaced with pin checking)
 	bool m_bus_conflict;
+	UINT8 m_open_bus;
 
 	// PRG
 	inline int prg_8k_bank_num(int bank);

src/mess/machine/nes_sunsoft.c

@@ -443,7 +443,7 @@ READ8_MEMBER(nes_sunsoft_4_device::read_m)
 	if (m_prgram && m_wram_enable)
 		return m_prgram[offset & (m_prgram_size - 1)];
 
-	return ((offset + 0x6000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 /*-------------------------------------------------
@@ -564,7 +564,7 @@ READ8_MEMBER(nes_sunsoft_fme7_device::read_m)
 			return m_prgram[((bank * 0x2000) + offset) & (m_prgram_size - 1)];
 	}
 
-	return ((offset + 0x6000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 

src/mess/machine/nes_sunsoft_dcs.c

@@ -231,7 +231,7 @@ READ8_MEMBER(nes_sunsoft_dcs_device::read_h)
 		if (m_timer_on)
 			return m_subslot->m_cart->read(space, offset, mem_mask);
 		else
-			return ((offset + 0x8000) & 0xff00) >> 8;   // after the timer is off, this returns open bus...
+			return m_open_bus;   // after the timer is off, this returns open bus...
 	}
 	else
 		return hi_access_rom(offset);
@@ -262,7 +262,7 @@ READ8_MEMBER(nes_sunsoft_dcs_device::read_m)
 	if (m_prgram && m_wram_enable)
 		return m_prgram[offset & (m_prgram_size - 1)];
 
-	return ((offset + 0x6000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 //-------------------------------------------------

src/mess/machine/nes_taito.c

@@ -366,7 +366,7 @@ READ8_MEMBER(nes_x1_005_device::read_m)
 	if (offset >= 0x1f00 && m_latch == 0xa3)
 		return m_x1_005_ram[offset & 0x7f];
 
-	return ((offset + 0x6000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }
 
 /*-------------------------------------------------
@@ -469,5 +469,5 @@ READ8_MEMBER(nes_x1_017_device::read_m)
 	if (offset < 0x1400 && m_reg[2] == 0x84)
 		return m_x1_017_ram[0x1000 + (offset & 0x3ff)];
 
-	return ((offset + 0x6000) & 0xff00) >> 8;   // open bus
+	return m_open_bus;   // open bus
 }