diff --git a/S7.Net/PLCHelpers.cs b/S7.Net/PLCHelpers.cs
index f2c757d..1668e08 100644
--- a/S7.Net/PLCHelpers.cs
+++ b/S7.Net/PLCHelpers.cs
@@ -1,4 +1,5 @@
 using S7.Net.Helper;
+using S7.Net.Protocol.S7;
 using S7.Net.Types;
 using System;
 using System.Collections.Generic;
@@ -14,7 +15,7 @@ namespace S7.Net
         /// </summary>
         /// <param name="amount"></param>
         /// <returns></returns>
-        private void BuildHeaderPackage(System.IO.MemoryStream stream, int amount = 1)
+        private static void BuildHeaderPackage(System.IO.MemoryStream stream, int amount = 1)
         {
             //header size = 19 bytes
             stream.WriteByteArray(new byte[] { 0x03, 0x00 });
@@ -37,7 +38,7 @@ namespace S7.Net
         /// <param name="startByteAdr">Start address of the byte</param>
         /// <param name="count">Number of bytes to be read</param>
         /// <returns></returns>
-        private void BuildReadDataRequestPackage(System.IO.MemoryStream stream, DataType dataType, int db, int startByteAdr, int count = 1)
+        private static void BuildReadDataRequestPackage(System.IO.MemoryStream stream, DataType dataType, int db, int startByteAdr, int count = 1)
         {
             //single data req = 12
             stream.WriteByteArray(new byte[] { 0x12, 0x0a, 0x10 });
@@ -176,7 +177,7 @@ namespace S7.Net
         /// <param name="varType"></param>
         /// <param name="varCount"></param>
         /// <returns>Byte lenght of variable</returns>
-        private int VarTypeToByteLength(VarType varType, int varCount = 1)
+        internal static int VarTypeToByteLength(VarType varType, int varCount = 1)
         {
             switch (varType)
             {
@@ -242,5 +243,20 @@ namespace S7.Net
                     offset++;
             }
         }
+
+        private static byte[] BuildReadRequestPackage(IList<DataItemAddress> dataItems)
+        {
+            int packageSize = 19 + (dataItems.Count * 12);
+            var package = new System.IO.MemoryStream(packageSize);
+
+            BuildHeaderPackage(package, dataItems.Count);
+
+            foreach (var dataItem in dataItems)
+            {
+                BuildReadDataRequestPackage(package, dataItem.DataType, dataItem.DB, dataItem.StartByteAddress, dataItem.ByteLength);
+            }
+
+            return package.ToArray();
+        }
     }
 }
diff --git a/S7.Net/PlcAsynchronous.cs b/S7.Net/PlcAsynchronous.cs
index fd3e6fd..b6b49c6 100644
--- a/S7.Net/PlcAsynchronous.cs
+++ b/S7.Net/PlcAsynchronous.cs
@@ -7,6 +7,7 @@ using System.Threading.Tasks;
 using S7.Net.Protocol;
 using System.IO;
 using System.Threading;
+using S7.Net.Protocol.S7;
 
 namespace S7.Net
 {
@@ -262,20 +263,10 @@ namespace S7.Net
 
             try
             {
-                // first create the header
-                int packageSize = 19 + (dataItems.Count * 12);
-                var package = new System.IO.MemoryStream(packageSize);
-                BuildHeaderPackage(package, dataItems.Count);
-                // package.Add(0x02);  // datenart
-                foreach (var dataItem in dataItems)
-                {
-                    BuildReadDataRequestPackage(package, dataItem.DataType, dataItem.DB, dataItem.StartByteAdr, VarTypeToByteLength(dataItem.VarType, dataItem.Count));
-                }
-
-                var dataToSend = package.ToArray();
+                var dataToSend = BuildReadRequestPackage(dataItems.Select(d => DataItem.GetDataItemAddress(d)).ToList());
                 await stream.WriteAsync(dataToSend, 0, dataToSend.Length);
 
-                var s7data = await COTP.TSDU.ReadAsync(stream, cancellationToken); //TODO use Async
+                var s7data = await COTP.TSDU.ReadAsync(stream, cancellationToken);
                 ValidateResponseCode((ReadWriteErrorCode)s7data[14]);
 
                 ParseDataIntoDataItems(s7data, dataItems);
@@ -295,6 +286,7 @@ namespace S7.Net
             return dataItems;
         }
 
+
         /// <summary>
         /// Write a number of bytes from a DB starting from a specified index. This handles more than 200 bytes with multiple requests.
         /// If the write was not successful, check LastErrorCode or LastErrorString.
@@ -444,14 +436,7 @@ namespace S7.Net
         {
             var stream = GetStreamIfAvailable();
 
-            // first create the header
-            int packageSize = 31; 
-            var package = new System.IO.MemoryStream(packageSize);
-            BuildHeaderPackage(package);
-            // package.Add(0x02);  // datenart
-            BuildReadDataRequestPackage(package, dataType, db, startByteAdr, count);
-
-            var dataToSend = package.ToArray();
+            var dataToSend = BuildReadRequestPackage(new [] { new DataItemAddress(dataType, db, startByteAdr, count)});
             await stream.WriteAsync(dataToSend, 0, dataToSend.Length, cancellationToken);
 
             var s7data = await COTP.TSDU.ReadAsync(stream, cancellationToken);
diff --git a/S7.Net/Protocol/S7/DataItemAddress.cs b/S7.Net/Protocol/S7/DataItemAddress.cs
new file mode 100644
index 0000000..cf37382
--- /dev/null
+++ b/S7.Net/Protocol/S7/DataItemAddress.cs
@@ -0,0 +1,37 @@
+namespace S7.Net.Protocol.S7
+{
+    /// <summary>
+    /// Represents an area of memory in the PLC
+    /// </summary>
+    internal class DataItemAddress
+    {
+        public DataItemAddress(DataType dataType, int db, int startByteAddress, int byteLength)
+        {
+            DataType = dataType;
+            DB = db;
+            StartByteAddress = startByteAddress;
+            ByteLength = byteLength;
+        }
+
+
+        /// <summary>
+        /// Memory area to read 
+        /// </summary>
+        public DataType DataType { get; }
+
+        /// <summary>
+        /// Address of memory area to read (example: for DB1 this value is 1, for T45 this value is 45)
+        /// </summary>
+        public int DB { get; }
+
+        /// <summary>
+        /// Address of the first byte to read
+        /// </summary>
+        public int StartByteAddress { get; }
+
+        /// <summary>
+        /// Length of data to read
+        /// </summary>
+        public int ByteLength { get; }
+    }
+}
diff --git a/S7.Net/Types/DataItem.cs b/S7.Net/Types/DataItem.cs
index c944ffa..254eab3 100644
--- a/S7.Net/Types/DataItem.cs
+++ b/S7.Net/Types/DataItem.cs
@@ -1,4 +1,5 @@
-using System;
+using S7.Net.Protocol.S7;
+using System;
 
 namespace S7.Net.Types
 {
@@ -94,5 +95,10 @@ namespace S7.Net.Types
 
             return dataItem;
         }
+
+        internal static DataItemAddress GetDataItemAddress(DataItem dataItem)
+        {
+            return new DataItemAddress(dataItem.DataType, dataItem.DB, dataItem.StartByteAdr, Plc.VarTypeToByteLength(dataItem.VarType, dataItem.Count));
+        }
     }
 }