Debugger:

. Improved break on FB or IO: account for slot empty (or not) & if expansion ROM enable
Memory:
. IORead_Cxxx(): Fix for Apple II support for when slot-3 is empty
. Apple II type was erroneously testing //e soft-switches

source/Debugger/Debug.cpp

@@ -8540,9 +8540,7 @@ void DebugContinueStepping ()
 
 			g_bDebugBreakpointHit = BP_HIT_NONE;
 
-			bool bPCIsFloatBusOrIO = (regs.pc >= 0xC000 && regs.pc <= 0xC0FF);	// TODO: Determine $C100..CFFF - assume executable
+			if ( MemIsAddrCodeMemory(regs.pc) )
-
-			if (!bPCIsFloatBusOrIO)
 			{
 				BYTE nOpcode = *(mem+regs.pc);
 
@@ -8555,7 +8553,7 @@ void DebugContinueStepping ()
 			}
 			else
 			{
-				g_bDebugBreakpointHit = BP_HIT_PC_READ_FLOATING_BUS_OR_IO_REG;
+				g_bDebugBreakpointHit = BP_HIT_PC_READ_FLOATING_BUS_OR_IO_MEM;
 			}
 
 			if (g_bDebugBreakpointHit)
@@ -8588,8 +8586,8 @@ void DebugContinueStepping ()
 				pszStopReason = TEXT("Register matches value");
 			else if (g_bDebugBreakpointHit & BP_HIT_MEM)
 				pszStopReason = TEXT("Memory accessed");
-			else if (g_bDebugBreakpointHit & BP_HIT_PC_READ_FLOATING_BUS_OR_IO_REG)
+			else if (g_bDebugBreakpointHit & BP_HIT_PC_READ_FLOATING_BUS_OR_IO_MEM)
-				pszStopReason = TEXT("PC reads from floating bus or I/O register");
+				pszStopReason = TEXT("PC reads from floating bus or I/O memory");
 			else
 				pszStopReason = TEXT("Unknown!");
 

source/Debugger/Debug.h

@@ -34,7 +34,7 @@
 		,BP_HIT_OPCODE  = (1 << 1)
 		,BP_HIT_REG     = (1 << 2)
 		,BP_HIT_MEM     = (1 << 3)
-		,BP_HIT_PC_READ_FLOATING_BUS_OR_IO_REG = (1 << 4)
+		,BP_HIT_PC_READ_FLOATING_BUS_OR_IO_MEM = (1 << 4)
 	};
 
 	extern int          g_nBreakpoints;

source/Memory.cpp

@@ -628,11 +628,14 @@ BYTE __stdcall IORead_Cxxx(WORD programcounter, WORD address, BYTE write, BYTE v
 
 	if (address >= APPLE_SLOT_BEGIN && address <= APPLE_SLOT_END)
 	{
-		// Fix for bug 18643 and bug 18886
 		const UINT uSlot = (address>>8)&0x7;
-		if ( (SW_SLOTCXROM) &&						// Peripheral (card) ROMs enabled in $C100..$C7FF
+		const bool bPeripheralSlotRomEnabled = IS_APPLE2 ? true	// A][
-		     !(!SW_SLOTC3ROM && uSlot == 3) &&		// Internal C3 ROM disabled in $C300 when slot == 3
+													     :		// A//e or above
-			 !IsCardInSlot(uSlot) )					// Slot is empty
+			  ( (SW_SLOTCXROM) &&					// Peripheral (card) ROMs enabled in $C100..$C7FF
+		      !(!SW_SLOTC3ROM  && uSlot == 3) );	// Internal C3 ROM disabled in $C300 when slot == 3
+
+		// Fix for bug 18643 and bug 18886
+		if (bPeripheralSlotRomEnabled && !IsCardInSlot(uSlot))	// Slot is empty
 		{
 			return IO_Null(programcounter, address, write, value, nCyclesLeft);
 		}
@@ -1106,6 +1109,40 @@ LPBYTE MemGetCxRomPeripheral()
 
 //===========================================================================
 
+// Post:
+// . true:  code memory
+// . false: I/O memory or floating bus
+bool MemIsAddrCodeMemory(const USHORT addr)
+{
+	if (addr < 0xC000 || addr > FIRMWARE_EXPANSION_END)	// Assume all A][ types have at least 48K
+		return true;
+
+	if (addr < APPLE_SLOT_BEGIN)		// [$C000..C0FF]
+		return false;
+
+	if (!IS_APPLE2 && !SW_SLOTCXROM)	// [$C100..CFFF] //e or Enhanced //e internal ROM
+		return true;
+
+	if (!IS_APPLE2 && !SW_SLOTC3ROM && (addr >> 8) == 0xC3)	// [$C300..C3FF] //e or Enhanced //e internal ROM
+		return true;
+
+	if (addr <= APPLE_SLOT_END)			// [$C100..C7FF]
+	{
+		const UINT uSlot = (addr >> 8) & 0x7;
+		if (!IsCardInSlot(uSlot))
+			return false;
+	}
+
+	// [$C800..CFFF]
+
+	if (g_eExpansionRomType == eExpRomNull)
+		return false;
+
+	return true;
+}
+
+//===========================================================================
+
 const UINT CxRomSize = 4*1024;
 const UINT Apple2RomSize = 12*1024;
 const UINT Apple2eRomSize = Apple2RomSize+CxRomSize;

source/Memory.h

@@ -44,6 +44,7 @@ LPBYTE  MemGetAuxPtr(const WORD);
 LPBYTE  MemGetMainPtr(const WORD);
 LPBYTE  MemGetBankPtr(const UINT nBank);
 LPBYTE  MemGetCxRomPeripheral();
+bool    MemIsAddrCodeMemory(const USHORT addr);
 void    MemInitialize ();
 void    MemInitializeROM(void);
 void    MemInitializeCustomF8ROM(void);