Industrial Communication Protocols

Hello Friends

While we are dealing with industries controls and automation, communication is must with high reliability, faster and redundancy for the safe and smooth operation. So for that Industries have given different standard communication protocols based on environment, hardware used and critical level.

So Industries have different communication protocols as below.

1. TCP/IP

2. Profinet

3. Profibus

4. RS 232

5. RS 485

6. Modbus

7. HART

8. AS-I

Here we are discussing about Industrial Automation so based on that we will understand the protocols. First we will see the communication systems Hierarchy. 

 Networking Levels of protocols are also different as per shown below.

1. TCP/IP :-

TCP/IP = Transmission Control Protocol/Internet Protocol is the basic communication language or protocol of the Internet. It can also be used as a communications protocol in the private networks ( intranets)

TCP/IP is a two-layered program

– Transmission Control Protocol - Manages the assembling of a message or file into smaller packets

– Internet Protocol- Handles the address part of each packet so that it gets to the right destination

2. Profinet

PROFINET is the open and innovative standard for industrial automation based on the industrial Ethernet, i.e. you can exchange process data with your machines as before but instead of using a fieldbus system, you use the Ethernet as the medium of communication.

The concept of the PROFINET satisfies all the requirements for industrial automation technology. You can use PROFINET for your factory and process automations that require response time under 100 milliseconds. Other applications, like drive technology applications or clock-synchronized Motion Control, can be served with response time up to less than 1 millisecond. For the purpose of running safety applications, you can use PROFIsafe, which is part of PROFINET. PROFINET technology is developed and published by PROFIBUS/PROFINET International e.V. (PI). It supplements the approved PROFIBUS technology, especially in terms of speed of data transmission and the use of Information Technology (IT). PROFINET uses IT standards such as TCP/IP and XML to communicate, configure and diagnose the machines or field devices.

3. Profibus

PROFIBUS offers functionally graduated communication protocols (Communication Profiles): DP and FMS. Depending on the application, the transmission technologies (Physical Profiles) RS-485, IEC 1158-2 or fiber optics are available. In the course of further technical development, the PROFIBUS User Organization is currently working on the implementation of universal concepts for vertical integration on the basis of TCP/IP. Application Profiles define the options of protocol and transmission technology required in the respective application area for the individual device types. These profiles also define vendor independent device behaviour. 

4. RS-232

The whole purpose of a serial interface is to provide a single path for data transmission wireless or over a cable. Parallel buses are still used in some applications. But with high-speed data so common today, a serial interface is the only practical option for communications over any distance greater than several feet.

Serial interfaces can be used to provide standardised logic levels from transmitters to receivers, define the transmission medium and connectors, and specify timing and data rates. In some cases, they can perform serial-to-parallel and parallel to- serial conversion or specify a basic data protocol.

5. RS-485

The 422 and 485 standards, as they are known today, are balanced data-transmission schemes that offer robust solutions for transmitting data over long distances and noisy environments. These standards don’t specify a logical communication protocol, and are used as the physical layer specification by many protocols such as Modbus, Profibus, DIN-Measurement-Bus and many others.

All Novus products that have serial bus communication follow RS485 standard, due to the advantages it shows in industrial environments. For being so well known all over the world, it is easily accepted. Besides they have been used for a long while, it is still common to find users with some unanswered questions about RS485 and RS422 based networks. Due to this, we propose this document to present a brief explanation on important topics for the design, analysis and installation of a communication networks using the RS485 and RS422 standards.

6. Modbus

MODBUS is a Master/Slave   communications protocol and developed by Gould-Modicon.

The protocol provides for one master device and up to 247 slave devices on a common line. Each device is assigned an address to distinguish it from all other connected device.

Only a master initiates a transaction. (query/response type,  or a broadcast/no-response type.) A transaction comprises a single query and single   response frame or a single broadcast frame.

Fixed characteristic : fixed such as frame format, frame  sequences, handling of communication errors and exception conditions, and the functions    performed.

Characteristic : choice of transmission media, baud rate, character parity, no. of stop bits and the transmission modes.

7. HART

Highway Addressable Remote Transducer

HART is a hybrid communications technology in which a modulated, two-way digital signal is imposed on the industry-standard 4–20 mA analog signal carrying the primary process variable.

The digital signal conveys additional process variables, device status and diagnostics information that can be routed to asset management, process control and safety systems.

This means that HART provides two simultaneous communication channels on the same wire–the industry standard 4–20 mA channel for fast, reliable and robust control (PV) and a digital channel for real-time communication of additional process/device information.

8. AS-I

The AS-I (Actuator Sensor Interface) is matched to the requirements in the lowest level.

AS-I operates actors and sensors with the first control level and replaces them with cable harnesses, distributor cabinets and connecting terminal plates.  Since then, the AS-I is an open standard.  In the meantime, many manufacturers offer intelligent, AS-I compatible actors and sensors in order to be able to transfer more information than only 1/0.

AS-I is especially easy in data manipulation. Field devices are simply clamped into cut terminal technology on an unprotected 2 way conductive flat cable.  As a result, the installation can then be accomplished  by people without any expertise.

AS-I is fast, simple, cost effective and also future safe because it meets more than half of the world market’s requirements for sensors from manufacturers that support it.