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namespace Q1.core.Arch;
// Big endian
public class Chip
{
public IAddressable Bus;
public u16 Pc, Sp;
public u16 Ax, Dx, Lx;
private u16[] _registers;
public void Reset()
{
this._registers = new u16[64];
this.Pc = ChipLayout.PROGRAM_START;
this.Sp = ChipLayout.STACK_START;
}
public void Clock()
{
this.Bus.Clock();
this.Fetch(out u8 opcode, out u8 m1, out u8 m2, out bool word);
switch (m1, m2)
{
case (0x00, 0x00):
InstructionSet.Lookup[opcode].Implicit.Execute(this, word);
break;
case (_, 0x00):
InstructionSet.Lookup[opcode].SimpleAddressing.Execute(this, m1, word);
break;
case (0x00, 0x01):
InstructionSet.Lookup[opcode].ExtendedImplicit.Execute(this, word);
break;
case (_, _):
InstructionSet.Lookup[opcode].ExtendedAddressing.Execute(this, m1, m2, word);
break;
}
}
/// [opcode: 7 bits] [word: 1 bits] [m1: 4 bits] [m2: 4 bits]
public void Fetch(out u8 opcode, out u8 m1, out u8 m2, out bool word)
{
u16 instruction = this.Bus.ReadWord(this.Pc);
this.Pc += 2;
opcode = (u8) ((instruction >> 8) & 0xFE); // 128 opcodes
word = ((instruction >> 8) & 0x1) != 0; // flag for word mode
m1 = (u8) ((instruction >> 4) & 0x0F); // 16 modes
m2 = (u8) (instruction & 0x0F); // 16 modes
}
public void SkipInstruction()
{
this.Fetch(out u8 _, out u8 m1, out u8 m2, out bool word);
this.Pc += (u8)(Size(m1, word) + Size(m2, word));
}
public u16 Load(u8 mode, bool word)
{
AddressingMode am = AddressingModes.Lookup[mode];
return word ? am.LoadWord(this) : am.LoadByte(this);
}
public void Store(u8 mode, u16 value, bool word)
{
AddressingMode am = AddressingModes.Lookup[mode];
if (word) am.StoreWord(this, value);
else am.StoreByte(this, (u8)(value & 0xFF));
}
public u8 Size(u8 mode, bool word)
{
AddressingMode am = AddressingModes.Lookup[mode];
return word ? am.SizeW : am.SizeB;
}
public void Push(u16 value)
{
if (this.Sp + 2 > ChipLayout.STACK_START + ChipLayout.STACK_SIZE)
throw new InvalidOperationException("Stack overflow");
this.Bus.WriteWord(this.Sp, value);
this.Sp += 2;
}
public u16 Pop()
{
if (this.Sp - 2 < ChipLayout.STACK_START)
throw new InvalidOperationException("Stack underflow");
this.Sp -= 2;
u16 value = this.Bus.ReadWord(this.Sp);
return value;
}
public u16 GetRegister(u8 index)
{
if (index < 64) return this._registers[index];
if (index == 0x40) return this.Ax;
if (index == 0x41) return (u16) (this.Ax >> 8); // High byte of Ax
if (index == 0x42) return (u16) (this.Ax & 0xFF); // Low byte of Ax
if (index == 0x44) return this.Dx;
if (index == 0x45) return (u16) (this.Dx >> 8); // High byte of Dx
if (index == 0x46) return (u16) (this.Dx & 0xFF); // Low byte of Dx
if (index == 0x48) return this.Lx;
if (index == 0x4C) return this.Pc;
if (index == 0x4D) return this.Sp;
throw new InvalidOperationException($"Invalid register index: {index}");
}
public void SetRegister(u8 index, u16 value)
{
if (index < 64) this._registers[index] = value;
else if (index == 0x40) this.Ax = value;
else if (index == 0x41) this.Ax = (u16)((this.Ax & 0x00FF) | ((value & 0xFF) << 8)); // Set high byte of Ax
else if (index == 0x42) this.Ax = (u16)((this.Ax & 0xFF00) | (value & 0xFF)); // Set low byte of Ax
else if (index == 0x44) this.Dx = value;
else if (index == 0x45) this.Dx = (u16)((this.Dx & 0x00FF) | ((value & 0xFF) << 8)); // Set high byte of Dx
else if (index == 0x46) this.Dx = (u16)((this.Dx & 0xFF00) | (value & 0xFF)); // Set low byte of Dx
else if (index == 0x48) this.Lx = value;
else if (index == 0x4C) this.Pc = value;
else if (index == 0x4D) this.Sp = value;
else throw new InvalidOperationException($"Invalid register index: {index}");
}
public void Interrupt(u16 code)
{
if (code >= ChipLayout.IVT_COUNT)
throw new InvalidOperationException($"Invalid interrupt code: {code}");
this.Push(this.Pc);
u16 interruptVectorAddress = (u16) (ChipLayout.IVT_START + code * 2);
this.Pc = this.Bus.ReadWord(interruptVectorAddress);
}
}
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