From 37180e18df2091a009c6d8bd051611deb7142643 Mon Sep 17 00:00:00 2001
From: "Darrell Spice, Jr" <darrell.spice.jr@spiceware.org>
Date: Thu, 24 Feb 2022 00:59:29 -0600
Subject: [PATCH] Fixed CDFJ+ issue if the first byte of the cartridge
 contained a value of FF_OFFSET thru FF_OFFSET + $23 (#879)

Updated Thumbulator's debug mode to allow run-time updating of the FF_OFFSET value.
---
 src/emucore/CartCDF.cxx     | 7 ++++---
 src/emucore/CartCDF.hxx     | 5 ++++-
 src/emucore/Thumbulator.cxx | 9 ++++++++-
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/src/emucore/CartCDF.cxx b/src/emucore/CartCDF.cxx
index 5504c3b2e..6dee96c40 100644
--- a/src/emucore/CartCDF.cxx
+++ b/src/emucore/CartCDF.cxx
@@ -153,8 +153,9 @@ void CartridgeCDF::setInitialState()
   // need to confirm with Chris
   myMode = 0xFF;
 
-  myBankOffset = myLDAXYimmediateOperandAddress = myJMPoperandAddress = 0;
+  myBankOffset = myJMPoperandAddress = 0;
   myFastJumpActive = myFastJumpStream = 0;
+  myLDAXYimmediateOperandAddress = LDAXY_OVERRIDE_INACTIVE;
 
   CartridgeARM::setInitialState();
 }
@@ -290,7 +291,7 @@ uInt8 CartridgeCDF::peek(uInt16 address)
                  && peekvalue <= myAmplitudeStream);
   if (fastfetch)
   {
-    myLDAXYimmediateOperandAddress = 0;
+    myLDAXYimmediateOperandAddress = LDAXY_OVERRIDE_INACTIVE;
     if (myFastFetcherOffset)
       peekvalue -= myRAM[myFastFetcherOffset]; // normalize peekvalue to 0 - 35
     if (peekvalue == myAmplitudeStream)
@@ -329,7 +330,7 @@ uInt8 CartridgeCDF::peek(uInt16 address)
       return readFromDatastream(peekvalue);
     }
   }
-  myLDAXYimmediateOperandAddress = 0;
+  myLDAXYimmediateOperandAddress = LDAXY_OVERRIDE_INACTIVE;
 
   // Switch banks if necessary
   switch(address)
diff --git a/src/emucore/CartCDF.hxx b/src/emucore/CartCDF.hxx
index 5a822311d..1ec6b5622 100644
--- a/src/emucore/CartCDF.hxx
+++ b/src/emucore/CartCDF.hxx
@@ -58,6 +58,9 @@ class System;
   @authors: Darrell Spice Jr, Chris Walton, Fred Quimby, John Champeau
             Thomas Jentzsch, Stephen Anthony, Bradford W. Mott
 */
+
+#define LDAXY_OVERRIDE_INACTIVE 0xFFFF
+
 class CartridgeCDF : public CartridgeARM
 {
   friend class CartridgeCDFWidget;
@@ -341,7 +344,7 @@ class CartridgeCDF : public CartridgeARM
 
     // set to address of #value if last byte peeked was A9 (LDA #),
     // or for CDFJ+ variations if A0 (LDY #) or A2 (LDX #)
-    uInt16 myLDAXYimmediateOperandAddress{0};
+    uInt16 myLDAXYimmediateOperandAddress{LDAXY_OVERRIDE_INACTIVE};
   
     // Some CDFJ+ drivers also override LDX # and/or LDY # for fast fetcher
     // use. These flag if this has been done.
diff --git a/src/emucore/Thumbulator.cxx b/src/emucore/Thumbulator.cxx
index 48c26ace9..a71f2cb5c 100644
--- a/src/emucore/Thumbulator.cxx
+++ b/src/emucore/Thumbulator.cxx
@@ -548,6 +548,11 @@ void Thumbulator::write32(uInt32 addr, uInt32 data)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 bool Thumbulator::isProtected(uInt32 addr)
 {
+  // Protected is within the driver RAM.
+  // For CDF variations parts of the driver RAM are reused to hold the
+  // datastream information, so is not protected.
+  // Additionally for CDFJ+ the Fast Fetcher offset is not write protected.
+  
   if (addr < 0x40000000) return false;
   addr -= 0x40000000;
 
@@ -562,9 +567,11 @@ bool Thumbulator::isProtected(uInt32 addr)
       return  (addr < 0x0800) && (addr > 0x0028) && !((addr >= 0x00a0) && (addr < (0x00a0 + 284)));
 
     case ConfigureFor::CDFJ:
-    case ConfigureFor::CDFJplus:
       return  (addr < 0x0800) && (addr > 0x0028) && !((addr >= 0x0098) && (addr < (0x0098 + 292)));
 
+    case ConfigureFor::CDFJplus:
+      return  (addr < 0x0800) && (addr > 0x0028) && !((addr >= 0x0098) && (addr < (0x0098 + 292))) && addr != 0x3E0;
+
     case ConfigureFor::BUS:
       return  (addr < 0x06d8) && (addr > 0x0028);
   }