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Fix 8080 implementation to be closer to Z80

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This commit is contained in:
Adrian Conlon
2026-03-21 09:48:35 +00:00
parent dcd98e5eb7
commit 0029427d6f
1 changed files with 87 additions and 45 deletions
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132
Intel8080/Intel8080.cs
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@@ -9,20 +9,34 @@ namespace Intel8080
using System;
using System.Diagnostics;
public class Intel8080(Bus bus, InputOutput ports) : IntelProcessor(bus)
public class Intel8080 : IntelProcessor
{
private readonly Register16 af = new();
public Intel8080(Bus bus, InputOutput ports)
: base(bus)
{
this._ports = ports;
this.RaisedPOWER += this.Intel8080_RaisedPOWER;
this.LoweredRESET += this.Intel8080_LoweredRESET;
this.LoweredINT += this.Intel8080_LoweredINT;
}
private readonly InputOutput ports = ports;
private bool _interruptPending;
private bool _resetPending;
private bool interruptEnable;
private readonly InputOutput _ports;
public InputOutput Ports => this._ports;
private readonly Register16 _af = new();
private bool _interruptEnable;
public override Register16 AF
{
get
{
this.af.Low = (byte)((this.af.Low | (byte)Bits.Bit1) & (int)~(Bits.Bit5 | Bits.Bit3));
return this.af;
this._af.Low = (byte)((this._af.Low | (byte)Bits.Bit1) & (int)~(Bits.Bit5 | Bits.Bit3));
return this._af;
}
}
@@ -48,21 +62,39 @@ namespace Intel8080
public override void PoweredStep()
{
if (this.RESET.Lowered())
if (this._resetPending)
{
this._resetPending = false;
this.HandleRESET();
return;
}
else if (this.INT.Lowered())
else if (this._interruptPending)
{
if (this.interruptEnable)
this._interruptPending = false;
if (this._interruptEnable)
{
this.HandleINT();
return;
}
}
else
{
this.Execute(this.FetchInstruction());
}
this.Execute(this.FetchInstruction());
}
private void Intel8080_RaisedPOWER(object? sender, EventArgs e)
{
this.DisableInterrupts();
this.ResetRegisterSet();
}
private void Intel8080_LoweredINT(object? sender, EventArgs e)
{
this._interruptPending = true;
}
private void Intel8080_LoweredRESET(object? sender, EventArgs e)
{
this._resetPending = true;
}
private void MemoryUpdate(int ticks)
@@ -192,9 +224,9 @@ namespace Intel8080
private void AdjustAuxiliaryCarrySub(byte before, byte value, int calculation) => this.F = AdjustAuxiliaryCarrySub(this.F, before, value, calculation);
protected override void DisableInterrupts() => this.interruptEnable = false;
protected override void DisableInterrupts() => this._interruptEnable = false;
protected override void EnableInterrupts() => this.interruptEnable = true;
protected override void EnableInterrupts() => this._interruptEnable = true;
private Register16 RP(int rp) => rp switch
{
@@ -284,10 +316,10 @@ namespace Intel8080
switch (q)
{
case 0: // LD rp,nn
this.RP(p).Assign(this.FetchWord());
this.FetchInto(this.RP(p));
break;
case 1: // ADD HL,rp
this.Add(this.RP(p));
this.HL.Assign(this.Add(this.HL, this.RP(p)));
this.Tick(7);
break;
default:
@@ -302,7 +334,7 @@ namespace Intel8080
switch (p)
{
case 0: // LD (BC),A
this.WriteMemoryIndirect(this.BC, this.A);
this.WriteMemoryIndirect(this.BC, this.A); //xxxx
break;
case 1: // LD (DE),A
this.WriteMemoryIndirect(this.DE, this.A);
@@ -365,14 +397,7 @@ namespace Intel8080
this.R(y, this.Decrement(this.R(y)), 2);
break;
case 6: // 8-bit load immediate
{
_ = this.FetchByte(); // LD r,n
if (memoryY)
{
this.Tick(2);
}
this.R(y, this.Bus.Data);
}
this.R(y, this.FetchByte(), 2);// LD r,n
break;
case 7: // Assorted operations on accumulator/flags
switch (y)
@@ -393,7 +418,7 @@ namespace Intel8080
this.DAA();
break;
case 5:
this.CMA();
this.CPL();
break;
case 6:
this.STC();
@@ -502,7 +527,8 @@ namespace Intel8080
this.WritePort(this.FetchByte());
break;
case 3: // IN A,(n)
this.A = this.ReadPort(this.FetchByte());
this.ReadPort(this.FetchByte());
this.A = this.Bus.Data;
break;
case 4: // EX (SP),HL
this.XHTL(this.HL);
@@ -597,7 +623,7 @@ namespace Intel8080
private byte Increment(byte operand)
{
var result = operand; ++operand;
var result = ++operand;
AdjustSZP(result);
ClearBit(StatusBits.AC, LowNibble(result));
return result;
@@ -605,7 +631,7 @@ namespace Intel8080
private byte Decrement(byte operand)
{
var result = operand; --operand;
var result = --operand;
AdjustSZP(result);
SetBit(StatusBits.AC, LowNibble(result) != (byte)Mask.Four);
return result;
@@ -634,11 +660,14 @@ namespace Intel8080
}
}
private void Add(Register16 value)
private Register16 Add(Register16 operand, Register16 value)
{
var result = this.HL.Word + value.Word;
this.HL.Word = (ushort)result;
SetBit(StatusBits.CF, result & (int)Bits.Bit16);
var addition = operand.Word + value.Word;
this.Intermediate.Word = (ushort)addition;
SetBit(StatusBits.CF, addition & (int)Bits.Bit16);
return this.Intermediate;
}
private byte Add(byte operand, byte value, int carry = 0)
@@ -742,8 +771,6 @@ namespace Intel8080
SetBit(StatusBits.CF, carry);
}
private void CMA() => this.A = (byte)~this.A;
private void STC() => SetBit(StatusBits.CF);
private void CMC() => ClearBit(StatusBits.CF, this.Carry());
@@ -763,32 +790,47 @@ namespace Intel8080
this.Tick(2);
}
#region Input/output port control
private void WritePort(Register16 port, byte data)
{
this.Bus.Data = data;
this.WritePort(port);
}
private void WritePort(byte port)
{
this.Bus.Address.Assign(port, this.A);
this.Bus.Data = this.A;
this.Bus.Address.Assign(port, this.Bus.Data = this.A);
this.WritePort();
}
private void WritePort()
{
this.Tick(3);
this.ports.Write(this.Bus.Address, this.Bus.Data);
this.Ports.Write(this.Bus.Address, this.Bus.Data);
this.Tick(1);
}
private byte ReadPort(byte port)
private void WritePort(Register16 port)
{
this.Bus.Address.Assign(port, this.A);
return this.ReadPort();
this.Bus.Address.Assign(port);
this.WritePort();
}
private byte ReadPort()
private void ReadPort(byte port)
{
this.Bus.Address.Assign(port, this.A);
this.ReadPort();
}
private void ReadPort()
{
this.Tick(2);
this.Bus.Data = this.ports.Read(this.Bus.Address);
this.Bus.Data = this.Ports.Read(this.Bus.Address);
this.Tick(2);
return this.Bus.Data;
}
#endregion
}
}