Implemented a load more Z80 OpCodes. Added IX, IY and Interrupts to Debugger

Core/Cpu/Z80.cs

@@ -11,8 +11,8 @@ namespace Core.Cpu
         public int InterruptMode { get; private set; } = 0; // Defaults to 0 on power-up
 
         // Interrupt Flip-Flops
-        public bool IFF1;
+        public bool IFF1 { get; private set; } = false;
-        public bool IFF2;
+        public bool IFF2 { get; private set; } = false;
 
         // Main Register Set
         public RegisterPair AF;
@@ -298,6 +298,17 @@ namespace Core.Cpu
             return (bits % 2) == 0;
         }
 
+        private void Push(ushort value)
+        {
+            // High byte goes first
+            SP--;
+            _memory.Write(SP, (byte)(value >> 8));
+
+            // Low byte goes second
+            SP--;
+            _memory.Write(SP, (byte)(value & 0xFF));
+        }
+
         private int ExecuteOpcode(byte opcode)
         {
             sbyte offset = 0;
@@ -311,6 +322,18 @@ namespace Core.Cpu
                 case 0x04: // INC B
                     BC.High = Inc8(BC.High);
                     return 4;
+                case 0x10: // DJNZ d
+                    sbyte djnzOffset = (sbyte)FetchByte();
+
+                    BC.High--; // Decrement the B register
+
+                    if (BC.High != 0)
+                    {
+                        PC = (ushort)(PC + djnzOffset);
+                        return 13; // Jump taken
+                    }
+
+                    return 8; // Loop finished, no jump
                 case 0x11: //LD DE, nn
                     DE.Word = FetchWord();
                     return 10;
@@ -366,6 +389,12 @@ namespace Core.Cpu
                         return 12; // Jump taken
                     }
                     return 7; // Jump not taken
+                case 0x32: // LD (nn), A
+                    {
+                        ushort destAddress = FetchWord();
+                        _memory.Write(destAddress, AF.High);
+                        return 13;
+                    }
                 case 0x35: // DEC (HL)
                            // Read the current byte from memory
                     byte memValue = _memory.Read(HL.Word);
@@ -394,6 +423,9 @@ namespace Core.Cpu
                 case 0x6B: // LD L, E
                     HL.Low = DE.Low;
                     return 4;
+                case 0x77: // LD (HL), A
+                    _memory.Write(HL.Word, AF.High);
+                    return 7;
                 case 0xA7: // AND A
                     And(AF.High);
                     return 4;
@@ -407,6 +439,11 @@ namespace Core.Cpu
                 case 0xC3:
                     PC = FetchWord();
                     return 10;
+                case 0xCD: // CALL nn
+                    ushort callAddress = FetchWord();
+                    Push(PC);
+                    PC = callAddress;
+                    return 17;
                 case 0xD3: // OUT (n), A
                     byte portOffset = FetchByte();
 
@@ -447,6 +484,10 @@ namespace Core.Cpu
                 case 0xF9: // LD SP, HL
                     SP = HL.Word; // (Use SP.Word = HL.Word if you made SP a RegisterPair)
                     return 6;
+                case 0xFB: // EI
+                    IFF1 = true;
+                    IFF2 = true;
+                    return 4;
                 case 0xFD:
                     return ExecuteFDPrefix();
                 default:
@@ -457,6 +498,7 @@ namespace Core.Cpu
         {
             // Fetch the actual extended instruction
             byte extendedOpcode = _memory.Read(PC++);
+            byte val = 0;
 
             switch (extendedOpcode)
             {
@@ -478,10 +520,37 @@ namespace Core.Cpu
                     return 20;
                 case 0x56: // IM 1
                     InterruptMode = 1;
-                    return 8; // Takes 8 T-States
+                    return 8;
+                case 0xB0: // LDIR
+                           // 1. Read byte from (HL)
+                    val = _memory.Read(HL.Word);
+
+                    // 2. Write byte to (DE)
+                    _memory.Write(DE.Word, val);
+
+                    // 3. Increment memory pointers, Decrement byte counter
+                    HL.Word++;
+                    DE.Word++;
+                    BC.Word--;
+
+                    // 4. Update Flags
+                    // Preserve S (0x80), Z (0x40), and C (0x01). 
+                    // H (0x10) and N (0x02) are always reset to 0.
+                    AF.Low &= 0xC1;
+
+                    // P/V Flag (Bit 2) is set to 1 if BC is not 0
+                    if (BC.Word != 0)
+                    {
+                        AF.Low |= 0x04;
+
+                        // Rewind the PC so the CPU executes this instruction again!
+                        PC -= 2;
+                        return 21; // Looping
+                    }
+                    return 16;
                 case 0xB8: // LDDR
                            // 1. Read byte from (HL)
-                    byte val = _memory.Read(HL.Word);
+                    val = _memory.Read(HL.Word);
 
                     // 2. Write byte to (DE)
                     _memory.Write(DE.Word, val);
@@ -515,13 +584,47 @@ namespace Core.Cpu
         private int ExecuteFDPrefix()
         {
             byte opcode = FetchByte();
+            ushort targetAddress = 0;
+            byte memVal = 0;
 
             switch (opcode)
             {
                 case 0x21: // LD IY, nn
                     IY.Word = FetchWord();
-                    return 14; // Takes 14 T-States
+                    return 14;
+                case 0x35: // DEC (IY+d)
+                    sbyte offset = (sbyte)FetchByte();
+                    targetAddress = (ushort)(IY.Word + offset);
 
+                    // Read, decrement using your existing helper, and write back
+                    memVal = _memory.Read(targetAddress);
+                    byte decVal = Dec8(memVal);
+                    _memory.Write(targetAddress, decVal);
+                    return 23;
+                case 0x75: // LD (IY+d), L                    
+                        sbyte offset75 = (sbyte)FetchByte();
+                        targetAddress = (ushort)(IY.Word + offset75);
+                        // Write the low byte of HL to memory
+                        _memory.Write(targetAddress, HL.Low);
+                        return 19;                    
+                case 0xCB: // The FD CB nested prefix
+                    {
+                        sbyte offsetCB = (sbyte)FetchByte(); // This is the '01'
+                        byte bitOpcode = FetchByte();        // This is the 'CE'
+                        targetAddress = (ushort)(IY.Word + offsetCB);
+
+                        switch (bitOpcode)
+                        {
+                            case 0xCE: // SET 1, (IY+d)
+                                memVal = _memory.Read(targetAddress);
+                                memVal |= 0x02; // 0x02 is Binary 0000 0010 (Bit 1)
+                                _memory.Write(targetAddress, memVal);
+                                return 23; // Takes 23 T-States
+
+                            default:
+                                throw new NotImplementedException($"FD CB opcode {bitOpcode:X2} not implemented!");
+                        }
+                    }
                 default:
                     throw new NotImplementedException($"FD prefix opcode {opcode:X2} not implemented!");
             }

Desktop/DebuggerForm.Designer.cs

@@ -50,94 +50,97 @@
             label2 = new Label();
             lblIX = new Label();
             lblIY = new Label();
+            lblIff1 = new Label();
+            lblIff2 = new Label();
+            lblIE = new Label();
             SuspendLayout();
             // 
             // lblAF
             // 
             lblAF.AutoSize = true;
-            lblAF.Location = new Point(12, 9);
+            lblAF.Location = new Point(10, 7);
             lblAF.Margin = new Padding(2, 0, 2, 0);
             lblAF.Name = "lblAF";
-            lblAF.Size = new Size(33, 25);
+            lblAF.Size = new Size(26, 20);
             lblAF.TabIndex = 0;
             lblAF.Text = "AF";
             // 
             // lblBC
             // 
             lblBC.AutoSize = true;
-            lblBC.Location = new Point(11, 60);
+            lblBC.Location = new Point(9, 48);
             lblBC.Margin = new Padding(2, 0, 2, 0);
             lblBC.Name = "lblBC";
-            lblBC.Size = new Size(33, 25);
+            lblBC.Size = new Size(27, 20);
             lblBC.TabIndex = 1;
             lblBC.Text = "BC";
             // 
             // lblDE
             // 
             lblDE.AutoSize = true;
-            lblDE.Location = new Point(12, 125);
+            lblDE.Location = new Point(10, 100);
             lblDE.Margin = new Padding(2, 0, 2, 0);
             lblDE.Name = "lblDE";
-            lblDE.Size = new Size(34, 25);
+            lblDE.Size = new Size(28, 20);
             lblDE.TabIndex = 2;
             lblDE.Text = "DE";
             // 
             // lblHL
             // 
             lblHL.AutoSize = true;
-            lblHL.Location = new Point(12, 188);
+            lblHL.Location = new Point(10, 150);
             lblHL.Margin = new Padding(2, 0, 2, 0);
             lblHL.Name = "lblHL";
-            lblHL.Size = new Size(33, 25);
+            lblHL.Size = new Size(27, 20);
             lblHL.TabIndex = 3;
             lblHL.Text = "HL";
             // 
             // lblPC
             // 
             lblPC.AutoSize = true;
-            lblPC.Location = new Point(11, 250);
+            lblPC.Location = new Point(9, 200);
             lblPC.Margin = new Padding(2, 0, 2, 0);
             lblPC.Name = "lblPC";
-            lblPC.Size = new Size(33, 25);
+            lblPC.Size = new Size(26, 20);
             lblPC.TabIndex = 4;
             lblPC.Text = "PC";
             // 
             // lblSP
             // 
             lblSP.AutoSize = true;
-            lblSP.Location = new Point(11, 315);
+            lblSP.Location = new Point(9, 252);
             lblSP.Margin = new Padding(2, 0, 2, 0);
             lblSP.Name = "lblSP";
-            lblSP.Size = new Size(32, 25);
+            lblSP.Size = new Size(25, 20);
             lblSP.TabIndex = 6;
             lblSP.Text = "SP";
             // 
             // lblFlags
             // 
             lblFlags.AutoSize = true;
-            lblFlags.Location = new Point(110, 65);
+            lblFlags.Location = new Point(88, 52);
             lblFlags.Margin = new Padding(2, 0, 2, 0);
             lblFlags.Name = "lblFlags";
-            lblFlags.Size = new Size(53, 25);
+            lblFlags.Size = new Size(43, 20);
             lblFlags.TabIndex = 7;
             lblFlags.Text = "Flags";
             // 
             // lblTStates
             // 
             lblTStates.AutoSize = true;
-            lblTStates.Location = new Point(110, 9);
+            lblTStates.Location = new Point(88, 7);
             lblTStates.Margin = new Padding(2, 0, 2, 0);
             lblTStates.Name = "lblTStates";
-            lblTStates.Size = new Size(75, 25);
+            lblTStates.Size = new Size(63, 20);
             lblTStates.TabIndex = 8;
             lblTStates.Text = "T-States";
             // 
             // txtMemoryStart
             // 
-            txtMemoryStart.Location = new Point(375, 26);
+            txtMemoryStart.Location = new Point(300, 21);
             txtMemoryStart.Margin = new Padding(2);
             txtMemoryStart.Name = "txtMemoryStart";
-            txtMemoryStart.Size = new Size(150, 31);
+            txtMemoryStart.Size = new Size(121, 27);
             txtMemoryStart.TabIndex = 9;
             txtMemoryStart.Text = "Memory Start";
             txtMemoryStart.TextAlign = HorizontalAlignment.Center;
@@ -145,10 +148,10 @@
             // 
             // btnStep
             // 
-            btnStep.Location = new Point(8, 523);
+            btnStep.Location = new Point(6, 418);
             btnStep.Margin = new Padding(2);
             btnStep.Name = "btnStep";
-            btnStep.Size = new Size(112, 34);
+            btnStep.Size = new Size(90, 27);
             btnStep.TabIndex = 12;
             btnStep.Text = "Step";
             btnStep.UseVisualStyleBackColor = true;
@@ -156,10 +159,10 @@
             // 
             // btnRun
             // 
-            btnRun.Location = new Point(149, 523);
+            btnRun.Location = new Point(119, 418);
             btnRun.Margin = new Padding(2);
             btnRun.Name = "btnRun";
-            btnRun.Size = new Size(112, 34);
+            btnRun.Size = new Size(90, 27);
             btnRun.TabIndex = 13;
             btnRun.Text = "Run";
             btnRun.UseVisualStyleBackColor = true;
@@ -167,10 +170,10 @@
             // 
             // btnRefreshMemory
             // 
-            btnRefreshMemory.Location = new Point(531, 26);
+            btnRefreshMemory.Location = new Point(425, 21);
             btnRefreshMemory.Margin = new Padding(2);
             btnRefreshMemory.Name = "btnRefreshMemory";
-            btnRefreshMemory.Size = new Size(112, 34);
+            btnRefreshMemory.Size = new Size(90, 27);
             btnRefreshMemory.TabIndex = 14;
             btnRefreshMemory.Text = "Refresh Memory";
             btnRefreshMemory.UseVisualStyleBackColor = true;
@@ -178,39 +181,37 @@
             // 
             // txtMemoryView
             // 
-            txtMemoryView.Location = new Point(110, 100);
+            txtMemoryView.Location = new Point(88, 80);
             txtMemoryView.Margin = new Padding(2);
             txtMemoryView.Name = "txtMemoryView";
-            txtMemoryView.Size = new Size(519, 243);
+            txtMemoryView.Size = new Size(416, 195);
             txtMemoryView.TabIndex = 15;
             txtMemoryView.Text = "Memory View Window";
             // 
             // lstDisassembly
             // 
             lstDisassembly.FormattingEnabled = true;
-            lstDisassembly.ItemHeight = 25;
+            lstDisassembly.Location = new Point(523, 11);
-            lstDisassembly.Location = new Point(654, 14);
             lstDisassembly.Margin = new Padding(2);
             lstDisassembly.Name = "lstDisassembly";
-            lstDisassembly.Size = new Size(314, 329);
+            lstDisassembly.Size = new Size(252, 264);
             lstDisassembly.TabIndex = 16;
             // 
             // lstStack
             // 
             lstStack.FormattingEnabled = true;
-            lstStack.ItemHeight = 25;
+            lstStack.Location = new Point(779, 11);
-            lstStack.Location = new Point(974, 14);
             lstStack.Margin = new Padding(2);
             lstStack.Name = "lstStack";
-            lstStack.Size = new Size(162, 329);
+            lstStack.Size = new Size(130, 264);
             lstStack.TabIndex = 17;
             // 
             // btnExit
             // 
-            btnExit.Location = new Point(1019, 520);
+            btnExit.Location = new Point(815, 416);
             btnExit.Margin = new Padding(2);
             btnExit.Name = "btnExit";
-            btnExit.Size = new Size(112, 34);
+            btnExit.Size = new Size(90, 27);
             btnExit.TabIndex = 18;
             btnExit.Text = "Full Exit";
             btnExit.UseVisualStyleBackColor = true;
@@ -219,54 +220,83 @@
             // label1
             // 
             label1.AutoSize = true;
-            label1.Location = new Point(361, 360);
+            label1.Location = new Point(200, 278);
-            label1.Margin = new Padding(4, 0, 4, 0);
             label1.Name = "label1";
-            label1.Size = new Size(97, 25);
+            label1.Size = new Size(81, 20);
             label1.TabIndex = 19;
             label1.Text = "Breakpoint";
             // 
             // txtBreakpoint
             // 
-            txtBreakpoint.Location = new Point(470, 351);
+            txtBreakpoint.Location = new Point(376, 281);
-            txtBreakpoint.Margin = new Padding(4, 4, 4, 4);
             txtBreakpoint.Name = "txtBreakpoint";
-            txtBreakpoint.Size = new Size(155, 31);
+            txtBreakpoint.Size = new Size(125, 27);
             txtBreakpoint.TabIndex = 20;
             // 
             // label2
             // 
             label2.AutoSize = true;
-            label2.Location = new Point(291, 26);
+            label2.Location = new Point(233, 21);
-            label2.Margin = new Padding(4, 0, 4, 0);
             label2.Name = "label2";
-            label2.Size = new Size(77, 25);
+            label2.Size = new Size(62, 20);
             label2.TabIndex = 21;
             label2.Text = "Address";
             // 
             // lblIX
             // 
             lblIX.AutoSize = true;
-            lblIX.Location = new Point(11, 373);
+            lblIX.Location = new Point(9, 298);
+            lblIX.Margin = new Padding(2, 0, 2, 0);
             lblIX.Name = "lblIX";
-            lblIX.Size = new Size(28, 25);
+            lblIX.Size = new Size(22, 20);
             lblIX.TabIndex = 22;
             lblIX.Text = "IX";
             // 
             // lblIY
             // 
             lblIY.AutoSize = true;
-            lblIY.Location = new Point(12, 430);
+            lblIY.Location = new Point(10, 344);
+            lblIY.Margin = new Padding(2, 0, 2, 0);
             lblIY.Name = "lblIY";
-            lblIY.Size = new Size(27, 25);
+            lblIY.Size = new Size(21, 20);
             lblIY.TabIndex = 23;
             lblIY.Text = "IY";
             // 
+            // lblIff1
+            // 
+            lblIff1.AutoSize = true;
+            lblIff1.Location = new Point(88, 298);
+            lblIff1.Name = "lblIff1";
+            lblIff1.Size = new Size(35, 20);
+            lblIff1.TabIndex = 24;
+            lblIff1.Text = "IFF1";
+            // 
+            // lblIff2
+            // 
+            lblIff2.AutoSize = true;
+            lblIff2.Location = new Point(88, 345);
+            lblIff2.Name = "lblIff2";
+            lblIff2.Size = new Size(35, 20);
+            lblIff2.TabIndex = 25;
+            lblIff2.Text = "IFF2";
+            // 
+            // lblIE
+            // 
+            lblIE.AutoSize = true;
+            lblIE.Location = new Point(200, 345);
+            lblIE.Name = "lblIE";
+            lblIE.Size = new Size(109, 20);
+            lblIE.TabIndex = 26;
+            lblIE.Text = "Interrupt Mode";
+            // 
             // DebuggerForm
             // 
-            AutoScaleDimensions = new SizeF(10F, 25F);
+            AutoScaleDimensions = new SizeF(8F, 20F);
             AutoScaleMode = AutoScaleMode.Font;
-            ClientSize = new Size(1160, 568);
+            ClientSize = new Size(928, 454);
+            Controls.Add(lblIE);
+            Controls.Add(lblIff2);
+            Controls.Add(lblIff1);
             Controls.Add(lblIY);
             Controls.Add(lblIX);
             Controls.Add(label2);
@@ -319,6 +349,9 @@
         private Label label2;
         private Label lblIX;
         private Label lblIY;
+        private Label lblIff1;
+        private Label lblIff2;
+        private Label lblIE;
         //private TextBox textBox4;
     }
 }

Desktop/DebuggerForm.cs

@@ -134,6 +134,9 @@ namespace Desktop
             lblSP.Text = $"SP: {_cpu.SP:X4}";
             lblIX.Text = $"IX: {_cpu.IX.Word:X4}";
             lblIY.Text = $"IY: {_cpu.IY.Word:X4}";
+            lblIff1.Text = $"IFF1: {_cpu.IFF1}";
+            lblIff2.Text = $"IFF2: {_cpu.IFF2}";
+            lblIE.Text = $"Interrupt Mode: {_cpu.InterruptMode}";
 
             // 2. Update Flags & T-States
             lblFlags.Text = $"Flags: {_cpu.GetFlagsString()}";
@@ -232,6 +235,12 @@ namespace Desktop
                     case 0x04:
                         mnemonic = "INC B";
                         break;
+                    case 0x10:
+                        sbyte djnzOffset = (sbyte)_memoryBus.Read((ushort)(currentPc + 1));
+                        ushort djnzDest = (ushort)(currentPc + 2 + djnzOffset);
+                        mnemonic = $"DJNZ 0x{djnzDest:X4}";
+                        instructionLength = 2;
+                        break;
                     case 0x11:
                         // LD DE, nn
                         byte deLow = _memoryBus.Read((ushort)(currentPc + 1));
@@ -285,6 +294,13 @@ namespace Desktop
                         mnemonic = $"JR NC, 0x{dest:X4}";
                         instructionLength = 2;
                         break;
+                    case 0x32:
+                        {
+                            ushort addr32 = (ushort)(_memoryBus.Read((ushort)(currentPc + 1)) | (_memoryBus.Read((ushort)(currentPc + 2)) << 8));
+                            mnemonic = $"LD (0x{addr32:X4}), A";
+                            instructionLength = 3;
+                            break;
+                        }
                     case 0x35:
                         mnemonic = "DEC (HL)";
                         break;
@@ -306,6 +322,9 @@ namespace Desktop
                     case 0x6B:
                         mnemonic = "LD L, E";
                         break;
+                    case 0x77:
+                        mnemonic = "LD (HL), A";
+                        break;
                     case 0xA7:
                         mnemonic = "AND A";
                         break;
@@ -322,6 +341,11 @@ namespace Desktop
                         mnemonic = $"JP 0x{jpHigh:X2}{jpLow:X2}";
                         instructionLength = 3;
                         break;
+                    case 0xCD:
+                            ushort callDest = (ushort)(_memoryBus.Read((ushort)(currentPc + 1)) | (_memoryBus.Read((ushort)(currentPc + 2)) << 8));
+                            mnemonic = $"CALL 0x{callDest:X4}";
+                            instructionLength = 3;
+                            break;
                     case 0xD3:
                         byte outPort = _memoryBus.Read((ushort)(currentPc + 1));
                         mnemonic = $"OUT (0x{outPort:X2}), A";
@@ -386,6 +410,9 @@ namespace Desktop
                     case 0xF9:
                         mnemonic = "LD SP, HL";
                         break;
+                    case 0xFB:
+                        mnemonic = "EI";
+                        break;
                     case 0xFD:
                         {
                             byte fdOpcode = _memoryBus.Read((ushort)(currentPc + 1));
@@ -396,6 +423,36 @@ namespace Desktop
                                 mnemonic = $"LD IY, 0x{iyVal:X4}";
                                 instructionLength = 4;
                             }
+                            else if (fdOpcode == 0x35) // DEC (IY+d)
+                            {
+                                sbyte d = (sbyte)_memoryBus.Read((ushort)(currentPc + 2));
+                                string sign = d >= 0 ? "+" : ""; // Gives us a clean + or - 
+                                mnemonic = $"DEC (IY{sign}{d})";
+                                instructionLength = 3;
+                            }
+                            else if (fdOpcode == 0xCB) // FD CB prefix
+                            {
+                                sbyte d = (sbyte)_memoryBus.Read((ushort)(currentPc + 2));
+                                byte cbOpcode = _memoryBus.Read((ushort)(currentPc + 3));
+                                string sign = d >= 0 ? "+" : "";
+
+                                if (cbOpcode == 0xCE)
+                                {
+                                    mnemonic = $"SET 1, (IY{sign}{d})";
+                                }
+                                else
+                                {
+                                    mnemonic = $"FD CB {d:X2} {cbOpcode:X2}"; // Fallback
+                                }
+                                instructionLength = 4;
+                            }
+                            else if (fdOpcode == 0x75) // LD (IY+d), L
+                            {
+                                sbyte d = (sbyte)_memoryBus.Read((ushort)(currentPc + 2));
+                                string sign = d >= 0 ? "+" : "";
+                                mnemonic = $"LD (IY{sign}{d}), L";
+                                instructionLength = 3;
+                            }
                             else
                             {
                                 mnemonic = $"FD PREFIX UNKNOWN (0x{fdOpcode:X2})";