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Added TAP file injection. Still incomplete.

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This commit is contained in:
Marc Parsons
2026-04-18 03:02:40 +01:00
parent 47f3a76bb2
commit c35bbda53f
6 changed files with 275 additions and 7 deletions
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152
Core/Cpu/Z80.cs
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@@ -40,11 +40,13 @@ namespace Core.Cpu
// The Memory Bus
private readonly IMemory _memory;
private readonly IO_Bus _simpleIoBus;
public TapManager _tapManager;
public Z80(IMemory memory, IO_Bus ioBus)
public Z80(IMemory memory, IO_Bus ioBus, TapManager tapManager)
{
_memory = memory;
_simpleIoBus = ioBus;
_tapManager = tapManager;
Reset();
}
@@ -129,6 +131,12 @@ namespace Core.Cpu
public int Step()
{
if (PC == 0x0556 && _tapManager.HasBlocks)
{
HandleInstantTapeLoad();
return 100; // Return a dummy number of T-States for the hijacking
}
// Fetch the next opcode and increment the Program Counter
byte opcode = _memory.Read(PC++);
int tStates = ExecuteOpcode(opcode);
@@ -138,6 +146,52 @@ namespace Core.Cpu
return tStates;
}
private void HandleInstantTapeLoad()
{
// 1. Grab the next block from the virtual cassette
byte[] block = _tapManager.GetNextBlock();
if (block == null) return; // Tape ended unexpectedly
// 2. Verify the block type.
// The ROM passes the expected flag (0x00 for Header, 0xFF for Data) in the A register.
byte expectedFlag = AF.High;
if (block[0] != expectedFlag)
{
// Tape loading error! Simulate a failure by clearing the Carry flag and returning.
AF.Low &= unchecked((byte)~0x01);
ExecuteRet();
return;
}
// 3. Copy the data block straight into the Spectrum's RAM!
// DE holds the number of bytes the ROM *wants*. We copy that much, skipping the Flag byte.
int bytesToCopy = DE.Word;
for (int i = 0; i < bytesToCopy; i++)
{
_memory.Write((ushort)(IX.Word + i), block[i + 1]);
}
// 4. Update the registers exactly how the ROM would after a successful load
IX.Word = (ushort)(IX.Word + bytesToCopy);
DE.Word = 0;
// 5. Set the Carry Flag to 1 (Success)
AF.Low |= 0x01;
// 6. Simulate a standard 'RET' instruction to exit the LD-BYTES routine safely
ExecuteRet();
}
// A quick helper to simulate a RET instruction manually
private void ExecuteRet()
{
byte pcLow = _memory.Read(SP);
SP++;
byte pcHigh = _memory.Read(SP);
SP++;
PC = (ushort)((pcHigh << 8) | pcLow);
}
// Reads a 16-bit word from the current PC (Little-Endian) and advances PC by 2
private ushort FetchWord()
{
@@ -1624,6 +1678,17 @@ namespace Core.Cpu
_memory.Write(address36, n36);
return 19;
case 0x5E: // LD E, (IX+d)
// 1. Fetch the displacement byte and cast it to a signed sbyte
sbyte offset5E = (sbyte)FetchByte();
// 2. Calculate the exact memory address (IX + offset)
ushort address5E = (ushort)(IX.Word + offset5E);
// 3. Read the byte from memory and drop it into the E register
DE.Low = _memory.Read(address5E);
return 19; // 19 T-States
case 0x74: // LD (IX+d), H
// 1. Fetch the displacement byte and cast it to a signed sbyte
sbyte offset74 = (sbyte)FetchByte();
@@ -1646,6 +1711,55 @@ namespace Core.Cpu
_memory.Write(address75, HL.Low);
return 19;
case 0x7E: // LD A, (IX+d)
// 1. Fetch the displacement byte and cast it to a signed sbyte
sbyte offset7E = (sbyte)FetchByte();
// 2. Calculate the exact memory address (IX + offset)
ushort address7E = (ushort)(IX.Word + offset7E);
// 3. Read the byte from memory and drop it straight into the Accumulator (A)
AF.High = _memory.Read(address7E);
return 19;
case 0xBE: // CP (IX+d)
// 1. Fetch the displacement byte and calculate the address
sbyte offsetBE = (sbyte)FetchByte();
ushort addressBE = (ushort)(IX.Word + offsetBE);
// 2. Read the value from memory
byte cpVal = _memory.Read(addressBE);
// 3. Perform the phantom subtraction
int aVal = AF.High;
result = aVal - cpVal;
// --- 8-Bit Compare Flag Calculation (Identical to SUB) ---
newFlags = 0;
// S Flag (Bit 7): Set if the phantom result is negative
if ((result & 0x80) != 0) newFlags |= 0x80;
// Z Flag (Bit 6): Set if A perfectly matches the memory value (A - value == 0)
if ((result & 0xFF) == 0) newFlags |= 0x40;
// H Flag (Bit 4): Set if there was a borrow from Bit 3
if (((aVal & 0x0F) - (cpVal & 0x0F)) < 0) newFlags |= 0x10;
// P/V Flag (Bit 2): Set on Overflow
if ((((aVal ^ cpVal) & (aVal ^ result)) & 0x80) != 0) newFlags |= 0x04;
// N Flag (Bit 1): Always set to 1 for Subtractions/Compares
newFlags |= 0x02;
// C Flag (Bit 0): Set if A was smaller than the memory value
if (aVal < cpVal) newFlags |= 0x01;
AF.Low = newFlags;
// CRITICAL: Notice we do NOT update AF.High! The Accumulator is preserved.
return 19; // 19 T-States
case 0xE1: // POP IX
// 1. Read the low byte from the top of the stack
byte popLow = _memory.Read(SP);
@@ -1875,6 +1989,42 @@ namespace Core.Cpu
AF.High = (byte)result;
return 19;
case 0xBE: // CP (IY+d)
// 1. Fetch the displacement byte and calculate the address using IY
sbyte offsetBE = (sbyte)FetchByte();
ushort addressBE = (ushort)(IY.Word + offsetBE);
// 2. Read the value from memory
byte cpVal = _memory.Read(addressBE);
// 3. Perform the phantom subtraction
aVal = AF.High;
result = aVal - cpVal;
// --- 8-Bit Compare Flag Calculation (Identical to SUB) ---
newFlags = 0;
// S Flag (Bit 7): Set if the phantom result is negative
if ((result & 0x80) != 0) newFlags |= 0x80;
// Z Flag (Bit 6): Set if A perfectly matches the memory value
if ((result & 0xFF) == 0) newFlags |= 0x40;
// H Flag (Bit 4): Set if there was a borrow from Bit 3
if (((aVal & 0x0F) - (cpVal & 0x0F)) < 0) newFlags |= 0x10;
// P/V Flag (Bit 2): Set on Overflow
if ((((aVal ^ cpVal) & (aVal ^ result)) & 0x80) != 0) newFlags |= 0x04;
// N Flag (Bit 1): Always set to 1 for Subtractions/Compares
newFlags |= 0x02;
// C Flag (Bit 0): Set if A was smaller than the memory value
if (aVal < cpVal) newFlags |= 0x01;
AF.Low = newFlags;
return 19; // 19 T-States
case 0xCB: // The FD CB nested prefix
{
sbyte displacement = (sbyte)FetchByte();

39
Core/Io/TapManager.cs Normal file
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@@ -0,0 +1,39 @@
using System;
using System.Collections.Generic;
namespace Core.Io
{
public class TapManager
{
private Queue<byte[]> _blocks = new Queue<byte[]>();
public void LoadTapData(byte[] fileData)
{
_blocks.Clear();
int position = 0;
while (position < fileData.Length)
{
// 1. Read the 16-bit block length (Little Endian)
int blockLength = fileData[position] | (fileData[position + 1] << 8);
position += 2;
// 2. Extract the block payload
byte[] blockData = new byte[blockLength];
Array.Copy(fileData, position, blockData, 0, blockLength);
position += blockLength;
// 3. Queue it up
_blocks.Enqueue(blockData);
}
}
public byte[] GetNextBlock()
{
return _blocks.Count > 0 ? _blocks.Dequeue() : null;
}
public bool HasBlocks => _blocks.Count > 0;
}
}

21
Desktop/DebuggerForm.cs
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@@ -850,6 +850,13 @@ namespace Desktop
mnemonic = $"LD (IX{sign}{d}), 0x{n:X2}";
instructionLength = 4;
}
else if (ddOpcode == 0x5E) // LD E, (IX+d)
{
sbyte d = (sbyte)_memoryBus.Read((ushort)(currentPc + 2));
string sign = d >= 0 ? "+" : "";
mnemonic = $"LD E, (IX{sign}{d})";
instructionLength = 3;
}
else if (ddOpcode == 0x74) // LD (IX+d), H
{
sbyte d = (sbyte)_memoryBus.Read((ushort)(currentPc + 2));
@@ -864,6 +871,20 @@ namespace Desktop
mnemonic = $"LD (IX{sign}{d}), L";
instructionLength = 3;
}
else if (ddOpcode == 0x7E) // LD A, (IX+d)
{
sbyte d = (sbyte)_memoryBus.Read((ushort)(currentPc + 2));
string sign = d >= 0 ? "+" : "";
mnemonic = $"LD A, (IX{sign}{d})";
instructionLength = 3;
}
else if (ddOpcode == 0xBE) // CP (IX+d)
{
sbyte d = (sbyte)_memoryBus.Read((ushort)(currentPc + 2));
string sign = d >= 0 ? "+" : "";
mnemonic = $"CP (IX{sign}{d})";
instructionLength = 3;
}
else if (ddOpcode == 0xE1) // POP IX
{
mnemonic = "POP IX";

43
Desktop/Form1.Designer.cs generated
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@@ -29,37 +29,72 @@
private void InitializeComponent()
{
picScreen = new PictureBox();
menuStrip1 = new MenuStrip();
fileToolStripMenuItem = new ToolStripMenuItem();
openToolStripMenuItem = new ToolStripMenuItem();
((System.ComponentModel.ISupportInitialize)picScreen).BeginInit();
menuStrip1.SuspendLayout();
SuspendLayout();
//
// picScreen
//
picScreen.Anchor = AnchorStyles.Top | AnchorStyles.Bottom | AnchorStyles.Left | AnchorStyles.Right;
picScreen.BackColor = Color.Black;
picScreen.Location = new Point(13, 13);
picScreen.Location = new Point(13, 33);
picScreen.Margin = new Padding(4);
picScreen.Name = "picScreen";
picScreen.Size = new Size(960, 768);
picScreen.Size = new Size(900, 720);
picScreen.SizeMode = PictureBoxSizeMode.Zoom;
picScreen.TabIndex = 0;
picScreen.TabStop = false;
//
// menuStrip1
//
menuStrip1.ImageScalingSize = new Size(24, 24);
menuStrip1.Items.AddRange(new ToolStripItem[] { fileToolStripMenuItem });
menuStrip1.Location = new Point(0, 0);
menuStrip1.Name = "menuStrip1";
menuStrip1.Size = new Size(922, 33);
menuStrip1.TabIndex = 1;
menuStrip1.Text = "menuStrip1";
//
// fileToolStripMenuItem
//
fileToolStripMenuItem.DropDownItems.AddRange(new ToolStripItem[] { openToolStripMenuItem });
fileToolStripMenuItem.Name = "fileToolStripMenuItem";
fileToolStripMenuItem.Size = new Size(54, 29);
fileToolStripMenuItem.Text = "File";
//
// openToolStripMenuItem
//
openToolStripMenuItem.Name = "openToolStripMenuItem";
openToolStripMenuItem.Size = new Size(158, 34);
openToolStripMenuItem.Text = "Open";
openToolStripMenuItem.Click += loadTAPToolStripMenuItem_Click;
//
// Form1
//
AutoScaleDimensions = new SizeF(10F, 25F);
AutoScaleMode = AutoScaleMode.Font;
ClientSize = new Size(987, 791);
ClientSize = new Size(922, 760);
Controls.Add(picScreen);
Controls.Add(menuStrip1);
KeyPreview = true;
MainMenuStrip = menuStrip1;
Margin = new Padding(4);
Name = "Form1";
Text = "Parsons Sinclair ZX Spectrum 48K - 2026";
((System.ComponentModel.ISupportInitialize)picScreen).EndInit();
menuStrip1.ResumeLayout(false);
menuStrip1.PerformLayout();
ResumeLayout(false);
PerformLayout();
}
#endregion
private PictureBox picScreen;
private MenuStrip menuStrip1;
private ToolStripMenuItem fileToolStripMenuItem;
private ToolStripMenuItem openToolStripMenuItem;
}
}

24
Desktop/Form1.cs
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@@ -14,6 +14,7 @@ namespace Desktop
private Z80 _cpu = null!;
private MemoryBus _memoryBus = null!;
private IO_Bus _simpleIoBus = null!;
private TapManager _tapManager = null!;
private int _ulaFrameCount = 0;
// The 16 physical colors of the ZX Spectrum (ARGB format)
@@ -52,12 +53,12 @@ namespace Desktop
{
_memoryBus = new MemoryBus();
_simpleIoBus = new IO_Bus();
_tapManager = new TapManager();
_memoryBus.CrapRAMData();
byte[] romData = RomLoader.Load("48.rom");
_memoryBus.LoadRom(romData);
_cpu = new Z80(_memoryBus, _simpleIoBus);
_cpu = new Z80(_memoryBus, _simpleIoBus, _tapManager);
// Pass 'this' so the DebuggerForm can talk back to this main window
DebuggerForm debugger = new DebuggerForm(_cpu, _memoryBus, this);
@@ -69,6 +70,25 @@ namespace Desktop
}
}
// Inside Desktop/Form1.cs
private void loadTAPToolStripMenuItem_Click(object sender, EventArgs e)
{
using (OpenFileDialog ofd = new OpenFileDialog())
{
ofd.Filter = "Spectrum TAP Files|*.tap";
if (ofd.ShowDialog() == DialogResult.OK)
{
// The Desktop UI reads the file from the hard drive
byte[] tapBytes = System.IO.File.ReadAllBytes(ofd.FileName);
// The pure Core logic processes the bytes
_cpu._tapManager.LoadTapData(tapBytes);
MessageBox.Show("Tape inserted! Type LOAD \"\" and press Enter.", "Tape Deck");
}
}
}
// Public so the Debugger's background thread can call it 50 times a second
public void RenderScreen()
{

3
Desktop/Form1.resx
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@@ -117,4 +117,7 @@
<resheader name="writer">
<value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
</resheader>
<metadata name="menuStrip1.TrayLocation" type="System.Drawing.Point, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a">
<value>17, 17</value>
</metadata>
</root>