From e8a1e7dc6e42406fedf5b3c0f1860b24914b5903 Mon Sep 17 00:00:00 2001
From: Adrian Conlon <adrian.conlon@gmail.com>
Date: Fri, 8 Aug 2025 21:47:48 +0100
Subject: [PATCH] Sort out Z80/Spectrum pin handling (again!)

---
 EightBit/IntelProcessor.cs |  2 ++
 Z80/Z80.cs                 | 36 ++++++++++++++++++++++++++++++------
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/EightBit/IntelProcessor.cs b/EightBit/IntelProcessor.cs
index 4355aa3..220ef53 100644
--- a/EightBit/IntelProcessor.cs
+++ b/EightBit/IntelProcessor.cs
@@ -70,6 +70,8 @@ namespace EightBit
             {
                 RaisingHALT?.Invoke(this, EventArgs.Empty);
                 this.HALT.Raise();
+                this.PC.Increment();
+                this.PC.Increment();
                 RaisedHALT?.Invoke(this, EventArgs.Empty);
             }
         }
diff --git a/Z80/Z80.cs b/Z80/Z80.cs
index 7634d67..54c59e3 100644
--- a/Z80/Z80.cs
+++ b/Z80/Z80.cs
@@ -13,8 +13,15 @@ namespace Z80
         {
             this._ports = ports;
             this.RaisedPOWER += this.Z80_RaisedPOWER;
+            this.LoweredRESET += this.Z80_LoweredRESET;
+            this.LoweredNMI += this.Z80_LoweredNMI;
+            this.LoweredINT += this.Z80_LoweredINT;
         }
 
+        private bool _interruptPending;
+        private bool _nonMaskableInterruptPending;
+        private bool _resetPending;
+
         private readonly InputOutput _ports;
 
         public InputOutput Ports => this._ports;
@@ -119,19 +126,21 @@ namespace Z80
             this._modifiedF = 0;
             this._displaced = this._prefixCB = this._prefixDD = this._prefixED = this._prefixFD = false;
 
-            if (this.RESET.Lowered())
+            if (this._resetPending)
             {
+                this._resetPending = false;
                 this.HandleRESET();
                 return;
             }
-            else if (this.NMI.Lowered())
+            else if (this._nonMaskableInterruptPending)
             {
+                this._nonMaskableInterruptPending = false;
                 this.HandleNMI();
                 return;
             }
-            else if (this.INT.Lowered())
+            else if (this._interruptPending)
             {
-                this.RaiseINT();
+                this._interruptPending = false;
                 this.RaiseHALT();
                 if (this.IFF1)
                 {
@@ -183,6 +192,20 @@ namespace Z80
             this.ExxAF();
             this.ResetRegisterSet();
         }
+        private void Z80_LoweredINT(object? sender, EventArgs e)
+        {
+            this._interruptPending = true;
+        }
+
+        private void Z80_LoweredNMI(object? sender, EventArgs e)
+        {
+            this._nonMaskableInterruptPending = true;
+        }
+
+        private void Z80_LoweredRESET(object? sender, EventArgs e)
+        {
+            this._resetPending = true;
+        }
 
         #region Z80 specific pins
 
@@ -514,8 +537,8 @@ namespace Z80
         protected override void HandleRESET()
         {
             base.HandleRESET();
+            this.DisableInterrupts();
             this.IV = this.REFRESH = 0;
-            this.IM = 0;
             this.SP.Word = this.AF.Word = (ushort)Mask.Sixteen;
             this.Tick(3);
         }
@@ -1564,9 +1587,10 @@ namespace Z80
 
         private void HandleNMI()
         {
-            this.IFF1 = false;
             this.RaiseNMI();
             this.RaiseHALT();
+            this.IFF2 = this.IFF1;
+            this.IFF1 = false;
             this.LowerM1();
             _ = this.Bus.Data;
             this.RaiseM1();