More vic-ii work

src/Dotnet6502.C64/Hardware/Vic2.cs

@@ -8,18 +8,30 @@ namespace Dotnet6502.C64.Hardware;
 public class Vic2
 {
     // Reference: https://zimmers.net/cbmpics/cbm/c64/vic-ii.txt
+    public enum GraphicsMode
+    {
+        StandardTextMode,
+        MulticolorTextMode,
+        StandardBitmapMode,
+        MulticolorBitmapMode,
+        EcmTextMode,
+        Invalid,
+    }
+
     private const int DotsPerCpuCycle = 8;
     private const int DotsPerScanline = 520;
-    private const int VisibleDotsPerScanLine = 418;
+    public const int VisibleDotsPerScanLine = 418;
     private const int TotalScanlines = 263;
     private const int FirstVisibleScanline = 28;
     private const int LastVisibleScanLine = 262;
     private const int FirstDisplayWindowScanLine = 51;
     private const int LastDisplayWindowScanLine = 250;
-    private const int VisibleScanLines = LastVisibleScanLine - FirstVisibleScanline + 1;
+    public const int VisibleScanLines = LastVisibleScanLine - FirstVisibleScanline + 1;
 
     private readonly IC64Display _c64Display;
     private readonly Memory<byte> _vic2Registers;
+    // private readonly Memory<byte> _colorRam;
+    private readonly ReadOnlyMemory<byte> _screenRam;
     private readonly RgbColor[] _frameBuffer = new RgbColor[VisibleDotsPerScanLine * VisibleScanLines];
     private readonly RgbColor[] _palette = new RgbColor[16];
     private int _lineCycleCount;
@@ -48,10 +60,12 @@ public class Vic2
     /// </summary>
     private ushort _videoMatrixLineIndex;
 
-    public Vic2(IC64Display c64Display, IoMemoryArea ioMemoryArea)
+    public Vic2(IC64Display c64Display, IoMemoryArea ioMemoryArea, ReadOnlyMemory<byte> screenRam)
     {
         _c64Display = c64Display;
+        _screenRam = screenRam;
         _vic2Registers = ioMemoryArea.Vic2Registers;
+        // _colorRam = ioMemoryArea.ColorRam;
 
         // Fill in the palette values based on the Colodore Palette
         _palette[0] = new RgbColor(0, 0, 0);       // Black
@@ -182,6 +196,13 @@ public class Vic2
         var firstBorderBottomLine = rsel ? 247 : 251;
         var borderColor = registerData.BorderColor;
 
+        // var colorRam = _colorRam.Span;
+        var screenRam = _screenRam.Span;
+
+        var row = (_currentScanLine - FirstVisibleScanline) / 8;
+        var rowInChar = (_currentScanLine - FirstVisibleScanline) % 8;
+        var column = _lineCycleCount - 17;
+
         // Write the next 8 dots
         for (var x = 0; x < DotsPerCpuCycle; x++)
         {
@@ -195,6 +216,11 @@ public class Vic2
                 _frameBuffer[pixelIndex] = _palette[borderColor];
                 continue;
             }
+
+            // Standard text only mode atm
+            var columnInChar = x;
+            var charCode = screenRam[row * 40 + column];
+            // var color = colorRam[row * 40 + column];
         }
     }
 
@@ -210,4 +236,26 @@ public class Vic2
                _currentScanLine <= 247 &&
                (_currentScanLine & 0b111) == registerData.YScroll;
     }
+
+    /// <summary>
+    /// Gets the current graphics mode based on the current register set
+    /// </summary>
+    /// <param name="registerData"></param>
+    /// <returns></returns>
+    private GraphicsMode GetGraphicsMode(Vic2RegisterData registerData)
+    {
+        var ecm = registerData.Ecm;
+        var bmm = registerData.Bmm;
+        var mcm = registerData.Mcm;
+
+        return (ecm, bmm, mcm) switch
+        {
+            (false, false, false) => GraphicsMode.StandardTextMode,
+            (false, false, true) => GraphicsMode.MulticolorTextMode,
+            (false, true, false) => GraphicsMode.StandardBitmapMode,
+            (false, true, true) => GraphicsMode.MulticolorBitmapMode,
+            (true, false, false) => GraphicsMode.EcmTextMode,
+            _ => GraphicsMode.Invalid,
+        };
+    }
 }

src/Dotnet6502.C64/Hardware/Vic2RegisterData.cs

@@ -49,6 +49,12 @@ public readonly ref struct Vic2RegisterData
     /// </summary>
     public byte CharacterMapPointer => (byte)((_registerBytes[VmCb] & 0xF) >> 1);
 
+    public bool Ecm => (_registerBytes[ControlRegister1] & 0b0100_0000) > 0;
+
+    public bool Bmm => (_registerBytes[ControlRegister1] & 0b0010_0000) > 0;
+
+    public bool Mcm => (_registerBytes[ControlRegister2] & 0b00010000) > 0;
+
     /// <summary>
     /// - 7   = Raster bit 8
     /// - 6   = ECM

src/Dotnet6502.C64/Integration/MonogameApp.cs

@@ -1,5 +1,6 @@
 using System.Diagnostics;
 using Dotnet6502.C64.Emulation;
+using Dotnet6502.C64.Hardware;
 using Microsoft.Xna.Framework;
 using Microsoft.Xna.Framework.Graphics;
 using Microsoft.Xna.Framework.Input;
@@ -8,8 +9,8 @@ namespace Dotnet6502.C64.Integration;
 
 public class MonogameApp : Game, IC64Display
 {
-    private const int Width = 464;
-    private const int Height = 247;
+    private const int Width = Vic2.VisibleDotsPerScanLine;
+    private const int Height = Vic2.VisibleScanLines;
 
     private readonly GraphicsDeviceManager _graphicsDeviceManager;
     private readonly object _synchronizationLock = new();

src/Dotnet6502.C64/Program.cs

@@ -11,9 +11,9 @@ var cliArgs = CommandLineHandler.Parse(args);
 Console.WriteLine("Starting Dotnet6502 Commodore64 emulator");
 var ioMemoryArea = new IoMemoryArea();
 var pla = await SetupPla(cliArgs);
-var memoryBus = SetupMemoryBus();
+var (memoryBus, screenRam) = SetupMemoryBus();
 var app = new MonogameApp(false);
-var vic2 = new Vic2(app, ioMemoryArea);
+var vic2 = new Vic2(app, ioMemoryArea, screenRam);
 var hal = new C64Hal(memoryBus, cancellationTokenSource.Token, vic2);
 var jitCustomizer = new C64JitCustomizer();
 var jitCompiler = new JitCompiler(hal, jitCustomizer, memoryBus);
@@ -66,19 +66,22 @@ async Task<ProgrammableLogicArray> SetupPla(CommandLineHandler.Values values)
     return programmableLogicArray;
 }
 
-MemoryBus SetupMemoryBus()
+(MemoryBus, ReadOnlyMemory<byte> screenRam) SetupMemoryBus()
 {
-    var memoryBus1 = new MemoryBus();
-    memoryBus1.Attach(pla, 0x0000);
-    pla.AttachToBus(memoryBus1);
+    var bus = new MemoryBus();
+    bus.Attach(pla, 0x0000);
+    pla.AttachToBus(bus);
 
     // fill in the rest with ram
-    memoryBus1.Attach(new BasicRamMemoryDevice(0x7fff - 0x0002 + 1), 0x0002);
-    memoryBus1.Attach(new BasicRamMemoryDevice(0xcfff - 0xc000 + 1), 0xc000);
+    var screenRamArea = new BasicRamMemoryDevice(0x07ff - 0x0400 + 1);
+    bus.Attach(new BasicRamMemoryDevice(0x03ff - 0x0002 + 1), 0x0002);
+    bus.Attach(screenRamArea, 0x0400);
+    bus.Attach(new BasicRamMemoryDevice(0x7fff - 0x0800 + 1), 0x0800);
+    bus.Attach(new BasicRamMemoryDevice(0xcfff - 0xc000 + 1), 0xc000);
 
     // TODO: Add cartridge rom low swapping to this region
-    memoryBus1.Attach(new BasicRamMemoryDevice(0x9fff - 0x8000 + 1), 0x8000);
-    return memoryBus1;
+    bus.Attach(new BasicRamMemoryDevice(0x9fff - 0x8000 + 1), 0x8000);
+    return (bus, screenRamArea.RawBlockFromZero!.Value);
 }
 
 async Task RunSystem()