From 8b1c405d95df1b831de73b1c71c238eddadfa720 Mon Sep 17 00:00:00 2001
From: g0me3 <cah4e3@gmail.com>
Date: Tue, 1 Oct 2019 22:01:30 +0300
Subject: [PATCH 1/3] mapper 15 chr protection implemented

---
 src/boards/15.cpp | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/src/boards/15.cpp b/src/boards/15.cpp
index 8ea05bf2..13ca2d7a 100644
--- a/src/boards/15.cpp
+++ b/src/boards/15.cpp
@@ -35,17 +35,17 @@ static SFORMAT StateRegs[] =
 static void Sync(void) {
 	int i;
 	setmirror(((latched >> 6) & 1) ^ 1);
-	switch (latchea) {
-	case 0x8000:
+	switch (latchea & 3) {
+	case 0:
 		for (i = 0; i < 4; i++)
 			setprg8(0x8000 + (i << 13), (((latched & 0x7F) << 1) + i) ^ (latched >> 7));
 		break;
-	case 0x8002:
+	case 2:
 		for (i = 0; i < 4; i++)
 			setprg8(0x8000 + (i << 13), ((latched & 0x7F) << 1) + (latched >> 7));
 		break;
-	case 0x8001:
-	case 0x8003:
+	case 1:
+	case 3:
 		for (i = 0; i < 4; i++) {
 			unsigned int b;
 			b = latched & 0x7F;
@@ -60,6 +60,18 @@ static void Sync(void) {
 static DECLFW(M15Write) {
 	latchea = A;
 	latched = V;
+	switch (latchea & 3) {
+	case 0:
+	case 3:
+		SetupCartCHRMapping(0, CHRptr[0], 0x2000, 0);
+		setchr8(0);
+		break;
+	case 1:
+	case 2:
+		SetupCartCHRMapping(0, CHRptr[0], 0x2000, 1);
+		setchr8(0);
+		break;
+	}
 	Sync();
 }
 
@@ -70,7 +82,6 @@ static void StateRestore(int version) {
 static void M15Power(void) {
 	latchea = 0x8000;
 	latched = 0;
-	setchr8(0);
 	setprg8r(0x10, 0x6000, 0);
 	SetReadHandler(0x6000, 0x7FFF, CartBR);
 	SetWriteHandler(0x6000, 0x7FFF, CartBW);

From 5ca7f608f7f173afefa586e25b3e3a174ba09ca3 Mon Sep 17 00:00:00 2001
From: norill <norill@wp.pl>
Date: Wed, 2 Oct 2019 18:30:36 +0200
Subject: [PATCH 2/3] Update 15.cpp

changes in accordance to the reverse-engineered mapper schematics:
- changed bank mode 1 mapping CPU $C000-$DFFF from "fixed to last bank" to "B OR 7" to support multiple 128KiB UNROM games in one cart
- latch D.7 bit ignored outside bank mode 2
- fixed latch D.6 bit interpreted as bank number bit
---
 src/boards/15.cpp | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/boards/15.cpp b/src/boards/15.cpp
index 13ca2d7a..5465a381 100644
--- a/src/boards/15.cpp
+++ b/src/boards/15.cpp
@@ -38,20 +38,20 @@ static void Sync(void) {
 	switch (latchea & 3) {
 	case 0:
 		for (i = 0; i < 4; i++)
-			setprg8(0x8000 + (i << 13), (((latched & 0x7F) << 1) + i) ^ (latched >> 7));
+			setprg8(0x8000 + (i << 13), ((latched & 0x3F) << 1) + i);
 		break;
 	case 2:
 		for (i = 0; i < 4; i++)
-			setprg8(0x8000 + (i << 13), ((latched & 0x7F) << 1) + (latched >> 7));
+			setprg8(0x8000 + (i << 13), ((latched & 0x3F) << 1) + (latched >> 7));
 		break;
 	case 1:
 	case 3:
 		for (i = 0; i < 4; i++) {
 			unsigned int b;
-			b = latched & 0x7F;
+			b = latched & 0x3F;
 			if (i >= 2 && !(latchea & 0x2))
-				b = 0x7F;
-			setprg8(0x8000 + (i << 13), (i & 1) + ((b << 1) ^ (latched >> 7)));
+				b = b | 0x07;
+			setprg8(0x8000 + (i << 13), (i & 1) + (b << 1));
 		}
 		break;
 	}

From 0fc18be6b8ef6b6ac73df93ade1172ae7d3e8df8 Mon Sep 17 00:00:00 2001
From: g0me3 <cah4e3@gmail.com>
Date: Wed, 2 Oct 2019 20:03:38 +0300
Subject: [PATCH 3/3] mapper 15 - fixed regression by previous fixes (waising /
 subors does not work properly with CHR write protection on mode 0)

---
 src/boards/15.cpp | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/src/boards/15.cpp b/src/boards/15.cpp
index 5465a381..01f55cd5 100644
--- a/src/boards/15.cpp
+++ b/src/boards/15.cpp
@@ -55,23 +55,19 @@ static void Sync(void) {
 		}
 		break;
 	}
+	setchr8(0);
 }
 
 static DECLFW(M15Write) {
 	latchea = A;
 	latched = V;
-	switch (latchea & 3) {
-	case 0:
-	case 3:
+	// cah4e3 02.10.19 once again, there may be either two similar mapper 15 exist. the one for 110in1 or 168in1 carts with complex multi game features.
+	// and another implified version for subor/waixing chinese originals and hacks with no different modes, working only in mode 0 and which does not
+	// expect there is any CHR write protection. protecting CHR writes only for mode 3 fixes the problem, all roms may be run on the same source again.
+	if((latchea & 3) == 3)
 		SetupCartCHRMapping(0, CHRptr[0], 0x2000, 0);
-		setchr8(0);
-		break;
-	case 1:
-	case 2:
+	else
 		SetupCartCHRMapping(0, CHRptr[0], 0x2000, 1);
-		setchr8(0);
-		break;
-	}
 	Sync();
 }