From f0ddb8caa8a26d9845b313f9132bc4bb2adb7af3 Mon Sep 17 00:00:00 2001
From: Thomas Jentzsch <tjentzsch@yahoo.de>
Date: Thu, 12 Sep 2019 11:08:26 +0200
Subject: [PATCH] partial fix for issue #537 (RAM writes to read port)

---
 src/emucore/Cart3E.cxx   | 17 +++++++++++++++--
 src/emucore/Cart4KSC.cxx | 15 +++++++++++++--
 src/emucore/CartBFSC.cxx | 15 +++++++++++++--
 src/emucore/CartEFSC.cxx | 15 +++++++++++++--
 src/emucore/CartF4SC.cxx | 15 +++++++++++++--
 src/emucore/CartF6SC.cxx | 15 +++++++++++++--
 src/emucore/CartF8SC.cxx | 15 +++++++++++++--
 7 files changed, 93 insertions(+), 14 deletions(-)

diff --git a/src/emucore/Cart3E.cxx b/src/emucore/Cart3E.cxx
index e8e1c77cd..67f9572c5 100644
--- a/src/emucore/Cart3E.cxx
+++ b/src/emucore/Cart3E.cxx
@@ -113,9 +113,22 @@ bool Cartridge3E::poke(uInt16 address, uInt8 value)
     return mySystem->tia().poke(address, value);
   }
   else
-    pokeRAM(myRAM[(address & 0x03FF) + ((myCurrentBank - 256) << 10)], pokeAddress, value);
+  {
+    if(address & 0x0400)
+    {
+      pokeRAM(myRAM[(address & 0x03FF) + ((myCurrentBank - 256) << 10)], pokeAddress, value);
+      return true;
+    }
+    else
+    {
+      // Writing to the read port should be ignored, but (TODO) trigger a break if option enabled
+      uInt8 dummy;
 
-  return true;
+      pokeRAM(dummy, pokeAddress, value);
+      return false;
+
+    }
+  }
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
diff --git a/src/emucore/Cart4KSC.cxx b/src/emucore/Cart4KSC.cxx
index 330c7dcdb..bf7c2c1bd 100644
--- a/src/emucore/Cart4KSC.cxx
+++ b/src/emucore/Cart4KSC.cxx
@@ -83,8 +83,19 @@ uInt8 Cartridge4KSC::peek(uInt16 address)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 bool Cartridge4KSC::poke(uInt16 address, uInt8 value)
 {
-  pokeRAM(myRAM[address & 0x007F], address, value);
-  return true;
+  if(address & 0x080)
+  {
+    pokeRAM(myRAM[address & 0x007F], address, value);
+    return true;
+  }
+  else
+  {
+    // Writing to the read port should be ignored, but (TODO) trigger a break if option enabled
+    uInt8 dummy;
+
+    pokeRAM(dummy, address, value);
+    return false;
+  }
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
diff --git a/src/emucore/CartBFSC.cxx b/src/emucore/CartBFSC.cxx
index d7edea29b..d41c290ce 100644
--- a/src/emucore/CartBFSC.cxx
+++ b/src/emucore/CartBFSC.cxx
@@ -98,8 +98,19 @@ bool CartridgeBFSC::poke(uInt16 address, uInt8 value)
     return false;
   }
 
-  pokeRAM(myRAM[address & 0x007F], pokeAddress, value);
-  return true;
+  if(address & 0x080)
+  {
+    pokeRAM(myRAM[address & 0x007F], pokeAddress, value);
+    return true;
+  }
+  else
+  {
+    // Writing to the read port should be ignored, but (TODO) trigger a break if option enabled
+    uInt8 dummy;
+
+    pokeRAM(dummy, pokeAddress, value);
+    return false;
+  }
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
diff --git a/src/emucore/CartEFSC.cxx b/src/emucore/CartEFSC.cxx
index 86c10a4af..0a5069489 100644
--- a/src/emucore/CartEFSC.cxx
+++ b/src/emucore/CartEFSC.cxx
@@ -98,8 +98,19 @@ bool CartridgeEFSC::poke(uInt16 address, uInt8 value)
     return false;
   }
 
-  pokeRAM(myRAM[address & 0x007F], pokeAddress, value);
-  return true;
+  if(address & 0x080)
+  {
+    pokeRAM(myRAM[address & 0x007F], pokeAddress, value);
+    return true;
+  }
+  else
+  {
+    // Writing to the read port should be ignored, but (TODO) trigger a break if option enabled
+    uInt8 dummy;
+
+    pokeRAM(dummy, pokeAddress, value);
+    return false;
+  }
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
diff --git a/src/emucore/CartF4SC.cxx b/src/emucore/CartF4SC.cxx
index 148d61d7d..9d468d28c 100644
--- a/src/emucore/CartF4SC.cxx
+++ b/src/emucore/CartF4SC.cxx
@@ -98,8 +98,19 @@ bool CartridgeF4SC::poke(uInt16 address, uInt8 value)
     return false;
   }
 
-  pokeRAM(myRAM[address & 0x007F], pokeAddress, value);
-  return true;
+  if(address & 0x080)
+  {
+    pokeRAM(myRAM[address & 0x007F], pokeAddress, value);
+    return true;
+  }
+  else
+  {
+    // Writing to the read port should be ignored, but (TODO) trigger a break if option enabled
+    uInt8 dummy;
+
+    pokeRAM(dummy, pokeAddress, value);
+    return false;
+  }
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
diff --git a/src/emucore/CartF6SC.cxx b/src/emucore/CartF6SC.cxx
index 3ad8ad790..b9f47ae89 100644
--- a/src/emucore/CartF6SC.cxx
+++ b/src/emucore/CartF6SC.cxx
@@ -138,8 +138,19 @@ bool CartridgeF6SC::poke(uInt16 address, uInt8 value)
       break;
   }
 
-  pokeRAM(myRAM[address & 0x007F], address, value);
-  return true;
+  if(address & 0x080)
+  {
+    pokeRAM(myRAM[address & 0x007F], address, value);
+    return true;
+  }
+  else
+  {
+    // Writing to the read port should be ignored, but (TODO) trigger a break if option enabled
+    uInt8 dummy;
+
+    pokeRAM(dummy, address, value);
+    return false;
+  }
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
diff --git a/src/emucore/CartF8SC.cxx b/src/emucore/CartF8SC.cxx
index 41da41178..5c4c8a523 100644
--- a/src/emucore/CartF8SC.cxx
+++ b/src/emucore/CartF8SC.cxx
@@ -118,8 +118,19 @@ bool CartridgeF8SC::poke(uInt16 address, uInt8 value)
       break;
   }
 
-  pokeRAM(myRAM[address & 0x007F], address, value);
-  return true;
+  if(address & 0x080)
+  {
+    pokeRAM(myRAM[address & 0x007F], address, value);
+    return true;
+  }
+  else
+  {
+    // Writing to the read port should be ignored, but (TODO) trigger a break if option enabled
+    uInt8 dummy;
+
+    pokeRAM(dummy, address, value);
+    return false;
+  }
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -