diff --git a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ULABase.cs b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ULABase.cs
index 657a255adf..d6e3b1ef66 100644
--- a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ULABase.cs
+++ b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ULABase.cs
@@ -69,11 +69,11 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
         /// <summary>
         /// T-State at which to start applying contention
         /// </summary>
-        protected int contentionStartPeriod;
+        public int contentionStartPeriod;
         /// <summary>
         /// T-State at which to end applying contention
         /// </summary>
-        protected int contentionEndPeriod;
+        public int contentionEndPeriod;
         /// <summary>
         /// T-State memory contention delay mapping
         /// </summary>
@@ -102,7 +102,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
         /// <summary>
         /// Table that stores T-State to screen/attribute address values
         /// </summary>
-        protected short[] floatingBusTable;
+        public short[] floatingBusTable;
         /// <summary>
         /// Cycle at which the last render update took place
         /// </summary>
diff --git a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ZXSpectrum48K/ZX48.Port.cs b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ZXSpectrum48K/ZX48.Port.cs
index c5bfd6f4d8..c8ad708a67 100644
--- a/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ZXSpectrum48K/ZX48.Port.cs
+++ b/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ZXSpectrum48K/ZX48.Port.cs
@@ -30,6 +30,8 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
             }
             else if (lowBitReset)
             {
+                CPU.TotalExecutedCycles += ULADevice.contentionTable[CurrentFrameCycle];
+
                 // Even I/O address so get input
                 // The high byte indicates which half-row of keys is being polled
                 /*
@@ -115,7 +117,27 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
                 // Kemptson Mouse
 
 
-                // if unused port the floating memory bus should be returned (still todo)
+                // if unused port the floating memory bus should be returned
+
+                // Floating bus is read on the previous cycle
+                int _tStates = CurrentFrameCycle - 1;
+
+                // if we are on the top or bottom border return 0xff
+                if ((_tStates < ULADevice.contentionStartPeriod) || (_tStates > ULADevice.contentionEndPeriod))
+                {
+                    result = 0xff;
+                }
+                else
+                {
+                    if (ULADevice.floatingBusTable[_tStates] < 0)
+                    {
+                        result = 0xff;
+                    }
+                    else
+                    {
+                        result = ReadBus((ushort)ULADevice.floatingBusTable[_tStates]);
+                    }
+                }
             }
 
             return (byte)result;