Water meter pulses overflow is handled properly (only 16-bit HW counter is used)

TestBenchFramework/BenchControl/Elde/RegisterReader/ReadRegisterOp.cs

@@ -14,7 +14,11 @@ namespace TBF.BenchControl.Elde.RegisterReader
 
 		/// Set by the constructor
 		readonly RegisterReader reader;
+        
         IntBox pulses;
+		int lastPulses;
+		bool lastPulsesValid;
+		
         IntBox refPulses;
 
 		/// <summary>
@@ -28,6 +32,7 @@ namespace TBF.BenchControl.Elde.RegisterReader
 			if (reader == null) throw new ArgumentNullException("reader is null or it is not Elde");
 
 			this.pulses = pulses;
+			lastPulsesValid = false;
 			log.Debug(this.ToString());
         }
 
@@ -46,7 +51,30 @@ namespace TBF.BenchControl.Elde.RegisterReader
 
 		private void ReadPulses()
 		{
-			pulses.Val = (int)reader.ControlBoard.WMeterPulses(reader.Position);
+			if (!lastPulsesValid)
+			{
+				lastPulses = (int)reader.ControlBoard.WMeterPulses(reader.Position);
+				lastPulsesValid = true;
+			}
+			else
+			{
+				UInt16 lowerWord = reader.ControlBoard.WMeterPulses(reader.Position);
+				int uncorrected = (int)(((uint)lastPulses & 0xFFFF0000) | lowerWord);
+				if (Math.Abs(uncorrected - lastPulses) <= Int16.MaxValue)
+				{
+					lastPulses = uncorrected;
+				}
+				else if (Math.Abs(uncorrected + 32768 - lastPulses) <= Int16.MaxValue)
+				{
+					lastPulses = uncorrected + 32768;
+				}
+				else if (Math.Abs(uncorrected - 32768 - lastPulses) <= Int16.MaxValue)
+				{
+					lastPulses = uncorrected - 32768;
+				}
+			}
+			pulses.Val = lastPulses;
+
 			if (refPulses != null)
 			{
 				refPulses.Val = (int)reader.ControlBoard.EtPulses(reader.Position);