Introduction

Communication ever was a very important task. In industries is not different. The automation control needs some

swap information between a large amount of devices.

With the fast development of communication systems, each manufacturer created it's own device driver, and it's

own protocol specification. This action turned impossible communication between all devices due incompatible protocols.

The SCADA(Supervisory Controle And Data Acquisition) systems was created to solve these problems. These

systems have various drivers to manage the communication between all devices from different manufacturers.

These systems was used since the creation of the OPC(OLE for Process Control) standard. OPC tries to create a

standard communication between all applications systems turning undispensable the driver use so, OPC works only

above the seventh layer of the ISO/OSI model.

The above image shows the complete communication process. OPC defines only methods and data type that can be used

between servers and clients communication.

All of OPC specifications are made by OPC Foundation. This page has an explanation about OPC.

A complete reference of the ISO/OSI model can be obtained at the Wikipedia.