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Everybody we communicate via the help of languages, without this language it’s very hard to convey our messages with each other. Exactly in the same way different automation devices are communicating with each other via standard communication protocols.

Today, in this article, we are going to study different PLC communication protocols. So further not waste more time and let’s start the topic.

Table of Contents

What is PLC Communication Protocol?

To know about PLC Communication protocols, first, we have to know what is communication protocol?

I like the definition of communication protocol as per startupandroid.com,

The communication protocol is a set of rules that sends and receives data between two or more communicating devices.

The communication protocol act as a way between devices to connect and communicate with each other. Without communication protocol devices are just only connected with each other but they can’t be communicated with each other.

So we can say that the communication protocols which PLC is using to communicate with different field devices, programming devices, other PLCs as well as controllers, HMIs, SCADAs, etc. are called PLC communication protocols.

List of Communication Protocols

AS-i – Actuator-sensor interface
BSAP – Bristol Standard Asynchronous Protocol
CC-Link Industrial Networks
CIP (Common Industrial Protocol)
ControlNet
DeviceNet
DF-1
DNP3
DirectNet
EtherCAT
Ethernet Global Data (EGD)
EtherNet/IP
Ethernet Powerlink
FINS
FOUNDATION Fieldbus – H1 & HSE
HART Protocol
HostLink Protocol
Interbus
MECHATROLINK
MelsecNet, and MelsecNet II, /B, and /H
Modbus PEMEX
Modbus Plus
Modbus RTU or ASCII or TCP
OSGP – The Open Smart Grid Protocol
OpenADR – Open Automated Demand Response
Optomux
PieP – An Open Fieldbus Protocol
Profibus
PROFINET
RAPIEnet
Honeywell SDS
SERCOS III
SERCOS interface
GE SRTP
Sinec H1
SynqNet
TTEthernet
MPI – Multi-Point Interface

reference from Wikipedia

This is the list of communication protocols used by different brands of PLCs as well as other control devices. You can buy the hardware required to communicate different automation devices from this link.

Important Parts of Communication Protocols

There are some important parts on which you can decide which communication protocol is best for your application, like

Baud Rate
Network Length
Number of nodes

Baud Rate ⇒

Baud Rate is the rate of transmission at which information is transferred in the communication channel. Baud rate is generally defined as the communication speed. The unit of baud rate is bps(bits per second).

Network Length ⇒

Network length is the total length of the network.

Number of nodes ⇒

Nodes represent the total number of devices connected to the network.

The below table represents the speed, length, and a maximum number of devices you can connect with this protocol.

Protocol	Baud Rate	Network Length	Number of nodes
Ethernet	100 Mb/s	100 m	255
Profibus	9.6 Kb/s – 12 Mb/s	1.2 km – 100 m	127
RS-232	19.2 Kb/s	10 m	1
RS-485	10 Mb/s	1.2 Km	32
MPI	19.2 – 38.4 Kb/s	50 m	32
PPI	187.5 Kb/s	500 m	1
DH	230.4 Kb/s	3.048 m	64
ControlNet	5 Mb/s	1000 m	99
DeviceNet	500 Kb/s	100 m	64

Which communication protocol you should use?

This primarily depends on the number of nodes or devices you want to connect and how much is your network length? The most commonly used communication protocol is Ethernet.

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⇒ What is PLC? How its work?

⇒ Sinking vs Sourcing in PLC

⇒ Bit Logic Instructions

⇒ PLC Timer and PLC Counter

⇒ Closed-loop vs Open-loop

⇒ PLC Programming Blocks

⇒ What is OPC? How does OPC work?

I hope you like this article about PLC communication protocols. If you have any questions then please comment down below. Each comment matters for us and gives us the motivation to share more knowledge with you all.

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