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Added AY38912 support

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This commit is contained in:
Marc Parsons
2026-04-30 14:35:12 +01:00
parent 3d13425d51
commit d90537de59
7 changed files with 223 additions and 29 deletions
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63
Core/Memory/MemoryBus.cs
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@@ -1,5 +1,6 @@
using System;
using Core.Interfaces;
using Core.Interfaces;
using System;
using System.Diagnostics;
namespace Core.Memory
{
@@ -46,6 +47,7 @@ namespace Core.Memory
// Called by the IO Bus when the CPU writes to a paging port
public void HandlePaging(ushort port, byte value)
{
Debug.WriteLine($"[PAGING] 0x7FFD Triggered! Hex: 0x{value:X2} | Bank: {value & 0x07}");
if (_pagingDisabled || _currentRomBank == 4) return; // Ignore if locked or in 48K mode
if (port == 0x7FFD)
@@ -65,33 +67,62 @@ namespace Core.Memory
_currentRomBank = (romHigh << 1) | romLow;
}
public byte Read(ushort address)
private int GetBankForSlot(int slot)
{
int slot = address >> 14; // Divide by 16384 to find Slot 0, 1, 2, or 3
int offset = address & 0x3FFF; // Find the exact byte inside that 16KB slot
// Amstrad +2A / +3 Special Paging Mode
bool specialPaging = (_port1FFD & 0x01) != 0;
if (specialPaging)
{
// Bits 1 and 2 dictate the specific Special RAM layout
int config = (_port1FFD >> 1) & 0x03;
switch (config)
{
case 0: return slot == 0 ? 0 : slot == 1 ? 1 : slot == 2 ? 2 : 3;
case 1: return slot == 0 ? 4 : slot == 1 ? 5 : slot == 2 ? 6 : 7;
case 2: return slot == 0 ? 4 : slot == 1 ? 5 : slot == 2 ? 6 : 3;
case 3: return slot == 0 ? 4 : slot == 1 ? 7 : slot == 2 ? 6 : 3;
}
}
// Standard 128K Paging
switch (slot)
{
case 0: return _romBanks[_currentRomBank][offset]; // 0x0000 - 0x3FFF (ROM)
case 1: return _ramBanks[5][offset]; // 0x4000 - 0x7FFF (Always RAM 5)
case 2: return _ramBanks[2][offset]; // 0x8000 - 0xBFFF (Always RAM 2)
case 3: return _ramBanks[_currentRamBankSlot3][offset]; // 0xC000 - 0xFFFF (Switchable RAM)
default: return 0xFF;
case 1: return 5;
case 2: return 2;
case 3: return _currentRamBankSlot3;
default: return -1; // -1 means it is pointing to a ROM chip!
}
}
public byte Read(ushort address)
{
int slot = address >> 14; // Find the 16KB Slot (0, 1, 2, or 3)
int offset = address & 0x3FFF;
int bank = GetBankForSlot(slot);
if (bank == -1)
{
return _romBanks[_currentRomBank][offset];
}
else
{
return _ramBanks[bank][offset];
}
}
public void Write(ushort address, byte value)
{
if (address < 0x4000) return; // Cannot write to ROM
int slot = address >> 14;
int offset = address & 0x3FFF;
switch (slot)
int bank = GetBankForSlot(slot);
// If the bank is NOT a ROM chip, we are allowed to write to it!
// (This allows the BIOS to write to 0x0000 during the self-test)
if (bank != -1)
{
case 1: _ramBanks[5][offset] = value; break;
case 2: _ramBanks[2][offset] = value; break;
case 3: _ramBanks[_currentRamBankSlot3][offset] = value; break;
_ramBanks[bank][offset] = value;
}
}