2017-02-07 update 1 Add comments and documents.

Modbus.Net/Modbus.Net.OPC/README.md

@@ -0,0 +1,35 @@
+Modbus.Net.OPC
+===================
+[![NuGet](https://img.shields.io/nuget/v/Modbus.Net.OPC.svg)](https://www.nuget.org/packages/Modbus.Net.OPC/)
+
+Modbus Implementation of Modbus.Net
+
+Table of Content:
+* [Basic Concept](#basic)
+* [Address Mapping](#address)
+* [Link](#link)
+##<a name="basic"></a> Basic Concept
+
+Siemens Protocal is derived by Profibus and Profinet.
+
+##<a name="address"></a> Address Mapping
+
+Modbus.Net.OPC has a simple address formatting tool. You can find it from AddressFormaterOPC.
+
+You need to use messages in BaseMachine and AddressUnit to create an OPC tag.
+
+Here is a Sample.
+
+If your tag is "1/15/Value_Opening", 1 is MachineId, 15 is StationId and Value_Opening is point name.
+
+Your tagGeter code should be.
+
+```C#
+(baseMachine, addressUnit) => return new string[]{baseMachine.Id, ((XXUnitExtend)addressUnit.unitExtend).stationId, addressUnit.Name};
+```
+
+If you want change your tag to "1.15.Value_Opening", just set the seperator to '.' .
+
+##<a name="link"></a> Link
+
+The link of OPC DA should like "opcda://PC-Name/OPC-Software-Name".