From 315ed8e040f5388e164313e30b43ae17a35abc57 Mon Sep 17 00:00:00 2001
From: Adrian Conlon <98398945+AdrianConlon@users.noreply.github.com>
Date: Sat, 14 Sep 2024 10:06:00 +0100
Subject: [PATCH] Work in progress to correct fixup effect storage

---
 M6502/M6502.cs     | 24 ++++++++++++++++++++++--
 M6502/M6502Core.cs | 11 +++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/M6502/M6502.cs b/M6502/M6502.cs
index edf93cd..64fd372 100644
--- a/M6502/M6502.cs
+++ b/M6502/M6502.cs
@@ -223,8 +223,28 @@ namespace EightBit
 
         private void StoreFixupEffect(byte data)
         {
-            var fixedAddress = (byte)(this.Bus.Address.High + 1);
-            this.MemoryWrite((byte)(data & fixedAddress));
+            ////var fixedAddress = (byte)(this.Bus.Address.High + 1);
+            //var fixedAddress = this.FixedPage + 1;
+            //var updated = (byte)(data & fixedAddress);
+            //if (this.Fixed)
+            //{
+            //    this.Bus.Address.High = updated;
+            //}
+
+            //this.MemoryWrite(updated);
+
+            byte updated;
+            if (this.Fixed)
+            {
+                updated = (byte)(data & this.FixedPage);
+                this.Bus.Address.High = updated;
+            }
+            else
+            {
+                updated = (byte)(data & this.UnfixedPage);
+                this.Bus.Address.High = updated;
+            }
+            this.MemoryWrite(updated);
         }
 
         private void SHA() => this.StoreFixupEffect((byte)(this.A & this.X));
diff --git a/M6502/M6502Core.cs b/M6502/M6502Core.cs
index a4542c7..5acfc5c 100644
--- a/M6502/M6502Core.cs
+++ b/M6502/M6502Core.cs
@@ -646,12 +646,22 @@ namespace EightBit
 
         private byte fixedPage;
 
+        private byte unfixedPage;
+
         public byte FixedPage
         {
             get => this.fixedPage;
             protected set => this.fixedPage = value;
         }
 
+        public byte UnfixedPage
+        {
+            get => this.unfixedPage;
+            protected set => this.unfixedPage = value;
+        }
+
+        public bool Fixed => this.FixedPage != this.UnfixedPage;
+
         protected void MaybeFixup()
         {
             if (this.Bus.Address.High != this.FixedPage)
@@ -685,6 +695,7 @@ namespace EightBit
 
         protected void NoteFixedAddress(ushort address)
         {
+            this.UnfixedPage = this.Bus.Address.High;
             this.Intermediate.Word = address;
             this.FixedPage = this.Intermediate.High;
             this.Bus.Address.Low = this.Intermediate.Low;