From 528c36e9c7b98403a8c3b2b954a19891e13fec6b Mon Sep 17 00:00:00 2001
From: 0kmg <9137159+0kmg@users.noreply.github.com>
Date: Mon, 2 Aug 2021 13:46:06 -0800
Subject: [PATCH] bus/nes: Enable menu access for a Contra/22-in-1 combo cart.

---
 hash/nes.xml                      |  4 +--
 src/devices/bus/nes/multigame.cpp | 57 +++++++++++++++++--------------
 src/devices/bus/nes/multigame.h   |  7 ++--
 3 files changed, 39 insertions(+), 29 deletions(-)

diff --git a/hash/nes.xml b/hash/nes.xml
index 68e739842ed..7e9730f5791 100644
--- a/hash/nes.xml
+++ b/hash/nes.xml
@@ -78461,14 +78461,14 @@ be better to redump them properly. -->
 		</part>
 	</software>
 
-	<software name="mc_22rb" supported="partial">
+	<software name="mc_22rb">
 		<description>22 in 1 (Reset Based)</description>
 		<year>19??</year>
 		<publisher>&lt;pirate&gt;</publisher>
+		<info name="usage" value="Press reset to use multigame menu."/>
 		<part name="cart" interface="nes_cart">
 			<feature name="slot" value="bmc_22games" />
 			<feature name="pcb" value="BMC-22GAMES" />
-			<feature name="mirroring" value="vertical" />
 			<dataarea name="prg" size="655360">
 				<rom name="22 in 1 (reset based).prg" size="655360" crc="03fdefad" sha1="4e84be9a20c5e385ae71c466a02613d5a74de01e" offset="00000" status="baddump" />
 			</dataarea>
diff --git a/src/devices/bus/nes/multigame.cpp b/src/devices/bus/nes/multigame.cpp
index 8ce1f8dfd58..1923ad4dfe7 100644
--- a/src/devices/bus/nes/multigame.cpp
+++ b/src/devices/bus/nes/multigame.cpp
@@ -301,8 +301,8 @@ nes_bmc_ball11_device::nes_bmc_ball11_device(const machine_config &mconfig, cons
 {
 }
 
-nes_bmc_22games_device::nes_bmc_22games_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
-	: nes_nrom_device(mconfig, NES_BMC_22GAMES, tag, owner, clock)
+nes_bmc_22games_device::nes_bmc_22games_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock)
+	: nes_nrom_device(mconfig, NES_BMC_22GAMES, tag, owner, clock), m_latch(0), m_reset(0)
 {
 }
 
@@ -851,14 +851,25 @@ void nes_bmc_ball11_device::pcb_reset()
 void nes_bmc_22games_device::device_start()
 {
 	common_start();
+	save_item(NAME(m_latch));
+	save_item(NAME(m_reset));
 }
 
 void nes_bmc_22games_device::pcb_reset()
 {
-	m_chr_source = m_vrom_chunks ? CHRROM : CHRRAM;
-	prg16_89ab(0);
-	prg16_cdef(7);
-	chr8(0, m_chr_source);
+	if (m_reset)
+	{
+		prg32(4);
+		m_latch = 1;
+	}
+	else
+	{
+		prg16_89ab(0);
+		prg16_cdef(7);
+		set_nt_mirroring(PPU_MIRROR_VERT);
+		m_reset = 1;
+	}
+	chr8(0, CHRRAM);
 }
 
 void nes_bmc_64y2k_device::device_start()
@@ -2278,37 +2289,33 @@ void nes_bmc_ball11_device::write_h(offs_t offset, u8 data)
  BMC-22GAMES
 
  Unknown Bootleg Multigame Board
- Games: 22 in 1
+ Games: Contra/22 in 1 combo
 
  iNES: mapper 230
 
- In MESS: Partially Supported. It would need a reset
- to work (not possible yet)
+ In MAME: Supported.
+
+ TODO: Determine whether reset works as written or
+ whether it toggles between Contra and the game menu.
+ Reset to Contra from the menu or other games often
+ fails due to RAM contents it seems.
 
  -------------------------------------------------*/
 
-void nes_bmc_22games_device::write_h(offs_t offset, uint8_t data)
+void nes_bmc_22games_device::write_h(offs_t offset, u8 data)
 {
 	LOG_MMC(("bmc_22games write_h, offset: %04x, data: %02x\n", offset, data));
 
-	if (1)  // this should flip at reset
+	if (m_latch)
 	{
-		prg16_89ab(data & 0x07);
-	}
-	else
-	{
-		if (data & 0x20)
-		{
-			prg16_89ab((data & 0x1f) + 8);
-			prg16_cdef((data & 0x1f) + 8);
-		}
-		else
-		{
-			prg16_89ab((data & 0x1f) + 8);
-			prg16_cdef((data & 0x1f) + 9);
-		}
+		u8 bank = (data & 0x1f) + 8;
+		u8 mode = !BIT(data, 5);
+		prg16_89ab(bank & ~mode);
+		prg16_cdef(bank | mode);
 		set_nt_mirroring(BIT(data, 6) ? PPU_MIRROR_VERT : PPU_MIRROR_HORZ);
 	}
+	else
+		prg16_89ab(data & 0x07);
 }
 
 /*-------------------------------------------------
diff --git a/src/devices/bus/nes/multigame.h b/src/devices/bus/nes/multigame.h
index 134bbc9a962..0d6453a28ff 100644
--- a/src/devices/bus/nes/multigame.h
+++ b/src/devices/bus/nes/multigame.h
@@ -675,15 +675,18 @@ class nes_bmc_22games_device : public nes_nrom_device
 {
 public:
 	// construction/destruction
-	nes_bmc_22games_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
+	nes_bmc_22games_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock);
 
-	virtual void write_h(offs_t offset, uint8_t data) override;
+	virtual void write_h(offs_t offset, u8 data) override;
 
 	virtual void pcb_reset() override;
 
 protected:
 	// device-level overrides
 	virtual void device_start() override;
+
+private:
+	int m_latch, m_reset;
 };