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Updated VDP to handle GameGear. Added Turbo mode. Versio 1.0 me thinks!

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This commit is contained in:
Marc Parsons
2026-05-18 14:57:19 +01:00
parent be43019fb0
commit 66f18d0510
5 changed files with 213 additions and 113 deletions
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123
Core/Video/SmsVdp.cs
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@@ -1,14 +1,15 @@
using System;
using System.Diagnostics;
using System.IO;
namespace Core.Video
{
public class SmsVdp
{
public bool IsPalRegion { get; set; } = false;
// The VDP's private memory! The CPU cannot touch these arrays directly.
public byte[] VRAM { get; private set; } = new byte[0x4000]; // 16KB Video RAM
public byte[] CRAM { get; private set; } = new byte[0x20]; // 32 Bytes Color Palette
public byte[] smsCRAM { get; private set; } = new byte[0x20]; // Master System - 32 Bytes colour Palette
public byte[] ggCRAM { get; private set; } = new byte[0x40]; // GameGear - 64 Bytes colour palette
public byte[] Registers { get; private set; } = new byte[16]; // 11 Hardware Control Registers
public int[] FrameBuffer { get; private set; } = new int[256 * 192];
private bool[] _priorityBuffer = new bool[256 * 192]; // Tracks priority pixels!
@@ -26,11 +27,14 @@ namespace Core.Video
private int _currentScanline = 0;
private int _lineCounter = 0;
private byte _statusRegister = 0x00;
public bool IsGameGear { get; set; } = false;
public bool InterruptPending =>
((_statusRegister & 0x80) != 0 && (Registers[1] & 0x20) != 0) || // VBlank
((_statusRegister & 0x40) != 0 && (Registers[0] & 0x10) != 0); // Line Interrupt
public byte ReadDataPort() // Port 0xBE
{
_isSecondControlByte = false; // Reading data resets the control latch
@@ -45,8 +49,8 @@ namespace Core.Video
_isSecondControlByte = false;
byte currentStatus = _statusRegister;
// CRITICAL HARDWARE QUIRK: Reading the status port physically
// clears the flags inside the chip! If we don't clear this,
// Reading the status port physically
// clears the flags inside the chip If we don't clear this,
// the interrupt line gets stuck on forever.
_statusRegister = 0x00;
@@ -56,20 +60,29 @@ namespace Core.Video
public void WriteDataPort(byte value) // Port 0xBE
{
_isSecondControlByte = false;
_readBuffer = value;
_readBuffer = value;
int address = _controlWord & 0x3FFF;
int command = (_controlWord >> 14) & 0x03;
if (command == 3) // Code 3: Write to Color Palette (CRAM)
if (command == 3) // Code 3: Write to Colour Palette (CRAM)
{
CRAM[address & 0x1F] = value;
if (IsGameGear)
{
ggCRAM[address & 0x3F] = value; // GG has 64 bytes of CRAM
}
else
{
smsCRAM[address & 0x1F] = value; // SMS has 32 bytes of CRAM
}
}
else // Code 0, 1, 2: Write to VRAM
else // THE FIX: Code 0, 1, 2: Write graphics to VRAM!
{
VRAM[address] = value;
}
_controlWord++; // Auto-increment so the Z80 can blast data fast
// THE FIX: The pointer MUST auto-increment so the CPU can blast data fast!
_controlWord++;
}
public void WriteControlPort(byte value) // Port 0xBF
@@ -105,23 +118,14 @@ namespace Core.Video
public byte ReadVCounter()
{
if (IsPalRegion)
{
// PAL Math: 313 lines. Counts 0 to 242, jumps to 186 (0xBA), counts to 255.
if (_currentScanline <= 242) return (byte)_currentScanline;
else return (byte)(_currentScanline - 57);
}
else
{
// NTSC Math: 262 lines. Counts 0 to 218, jumps to 213 (0xD5), counts to 255.
// NTSC Math: 262 lines. Counts 0 to 218, jumps to 213 (0xD5), counts to 255.
if (_currentScanline <= 218) return (byte)_currentScanline;
else return (byte)(_currentScanline - 6);
}
}
public byte ReadHCounter()
{
// The Master System H-Counter is a notoriously weird 8-bit timer.
// It counts from 0x00 to 0x93, then jumps forward to 0xE9, ending at 0xFF.
// The Master System H-Counter counts from 0x00 to 0x93, then jumps forward to 0xE9, ending at 0xFF.
// 1 T-State = 1.5 pixels. The H-Counter increments every 2 pixels.
// So H = T * 0.75
@@ -173,7 +177,7 @@ namespace Core.Video
// 3. MOVE TO THE NEXT LINE
_currentScanline++;
int maxLines = IsPalRegion ? 313 : 262;
int maxLines = 262;
if (_currentScanline > maxLines -1)
{
@@ -197,7 +201,6 @@ namespace Core.Video
for (int x = 0; x < 256; x++) FrameBuffer[(screenY * 256) + x] = unchecked((int)0xFF000000);
return;
}
// --- 1. RENDER BACKGROUND LINE ---
ushort nameTableBase = (ushort)((Registers[2] & 0x0E) << 10);
int scrollX = Registers[8];
@@ -213,16 +216,10 @@ namespace Core.Video
// --- LEFT COLUMN MASKING (OVERSCAN CURTAIN) ---
if (maskLeftCol && screenX < 8)
{
// Draw the physical backdrop color (from Sprite Palette + Reg 7 index)
byte bgSmsColor = CRAM[16 + (Registers[7] & 0x0F)];
int bgR = (bgSmsColor & 0x03) * 85;
int bgG = ((bgSmsColor >> 2) & 0x03) * 85;
int bgB = ((bgSmsColor >> 4) & 0x03) * 85;
// REPLACE THE R/G/B MATH WITH THIS SINGLE LINE:
int bgAddress = (screenY * 256) + screenX;
FrameBuffer[bgAddress] = (255 << 24) | (bgR << 16) | (bgG << 8) | bgB;
FrameBuffer[bgAddress] = GetRgbColour(16, Registers[7] & 0x0F);
// Flag it as priority so sprites also hide behind the curtain!
_priorityBuffer[bgAddress] = true;
continue;
}
@@ -261,21 +258,17 @@ namespace Core.Video
byte bp3 = VRAM[tileAddress + (readY * 4) + 3];
int readX = flipH ? tileX : (7 - tileX);
int colorIndex = ((bp0 >> readX) & 1) | (((bp1 >> readX) & 1) << 1) |
int colourIndex = ((bp0 >> readX) & 1) | (((bp1 >> readX) & 1) << 1) |
(((bp2 >> readX) & 1) << 2) | (((bp3 >> readX) & 1) << 3);
int paletteOffset = useSpritePalette ? 16 : 0;
byte smsColor = CRAM[paletteOffset + colorIndex];
int r = (smsColor & 0x03) * 85;
int g = ((smsColor >> 2) & 0x03) * 85;
int b = ((smsColor >> 4) & 0x03) * 85;
int finalColour = GetRgbColour(paletteOffset, colourIndex);
int screenAddress = (screenY * 256) + screenX;
// Draw background and reset priority mask for this exact pixel
FrameBuffer[screenAddress] = (255 << 24) | (r << 16) | (g << 8) | b;
_priorityBuffer[screenAddress] = (priority && colorIndex != 0);
FrameBuffer[screenAddress] = finalColour;
_priorityBuffer[screenAddress] = (priority && colourIndex != 0);
}
// --- 2. RENDER SPRITE LINE ---
@@ -329,24 +322,53 @@ namespace Core.Video
if (_priorityBuffer[(screenY * 256) + screenX]) continue;
int shift = 7 - px;
int colorIndex = ((bp0 >> shift) & 1) | (((bp1 >> shift) & 1) << 1) |
int colourIndex = ((bp0 >> shift) & 1) | (((bp1 >> shift) & 1) << 1) |
(((bp2 >> shift) & 1) << 2) | (((bp3 >> shift) & 1) << 3);
if (colorIndex == 0) continue;
if (colourIndex == 0) continue;
byte smsColor = CRAM[16 + colorIndex];
int r = (smsColor & 0x03) * 85;
int g = ((smsColor >> 2) & 0x03) * 85;
int b = ((smsColor >> 4) & 0x03) * 85;
FrameBuffer[(screenY * 256) + screenX] = (255 << 24) | (r << 16) | (g << 8) | b;
// REPLACE THE R/G/B MATH WITH THIS SINGLE LINE:
FrameBuffer[(screenY * 256) + screenX] = GetRgbColour(16, colourIndex);
}
}
}
public int GetRgbColour(int paletteOffset, int colourIndex)
{
//Debug.WriteLine(_isGameGear);
int r, g, b;
if (IsGameGear)
{
// Game Gear: 2 bytes per colour. Format: ----BBBBGGGGRRRR
int cramIndex = (paletteOffset + colourIndex) * 2;
ushort ggcolour = (ushort)(ggCRAM[cramIndex] | (ggCRAM[cramIndex + 1] << 8));
// Extract 4-bit values (0-15) and map them to standard 8-bit values (0-255).
// We multiply by 17 because 255 / 15 = 17!
r = (ggcolour & 0x0F) * 17;
g = ((ggcolour >> 4) & 0x0F) * 17;
b = ((ggcolour >> 8) & 0x0F) * 17;
}
else
{
// Master System: 1 byte per colour. Format: --BBGGRR
byte smscolour = smsCRAM[paletteOffset + colourIndex];
// Extract 2-bit values (0-3) and map them to standard 8-bit values (0-255).
// We multiply by 85 because 255 / 3 = 85!
r = (smscolour & 0x03) * 85;
g = ((smscolour >> 2) & 0x03) * 85;
b = ((smscolour >> 4) & 0x03) * 85;
}
return (255 << 24) | (r << 16) | (g << 8) | b;
}
public void SaveState(BinaryWriter bw)
{
bw.Write(VRAM);
bw.Write(CRAM);
bw.Write(smsCRAM);
bw.Write(ggCRAM);
bw.Write(Registers);
bw.Write(_isSecondControlByte);
bw.Write(_controlWord);
@@ -359,12 +381,14 @@ namespace Core.Video
// ADD THESE:
bw.Write(_latchedHScroll);
bw.Write(_latchedVScroll);
bw.Write(IsGameGear);
}
public void LoadState(BinaryReader br)
{
Array.Copy(br.ReadBytes(VRAM.Length), VRAM, VRAM.Length);
Array.Copy(br.ReadBytes(CRAM.Length), CRAM, CRAM.Length);
Array.Copy(br.ReadBytes(smsCRAM.Length), smsCRAM, smsCRAM.Length);
Array.Copy(br.ReadBytes(ggCRAM.Length), ggCRAM, ggCRAM.Length);
Array.Copy(br.ReadBytes(Registers.Length), Registers, Registers.Length);
_isSecondControlByte = br.ReadBoolean();
_controlWord = br.ReadUInt16();
@@ -377,6 +401,7 @@ namespace Core.Video
// ADD THESE:
_latchedHScroll = br.ReadInt32();
_latchedVScroll = br.ReadInt32();
IsGameGear = br.ReadBoolean();
}
}
}