30+ Most Useful PLC Communication Protocols

Hi! Programmers! How are you? I hope you all are good and doing well in your life.

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.

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.

communication protocols

List of Communication Protocols

  1. AS-i – Actuator-sensor interface
  2. BSAP – Bristol Standard Asynchronous Protocol
  3. CC-Link Industrial Networks
  4. CIP (Common Industrial Protocol)
  5. ControlNet
  6. DeviceNet
  7. DF-1
  8. DNP3
  9. DirectNet
  10. EtherCAT
  11. Ethernet Global Data (EGD)
  12. EtherNet/IP
  13. Ethernet Powerlink
  14. FINS
  15. FOUNDATION Fieldbus – H1 & HSE
  16. HART Protocol
  17. HostLink Protocol
  18. Interbus
  20. MelsecNet, and MelsecNet II, /B, and /H
  21. Modbus PEMEX
  22. Modbus Plus
  23. Modbus RTU or ASCII or TCP
  24. OSGP – The Open Smart Grid Protocol
  25. OpenADR – Open Automated Demand Response
  26. Optomux
  27. PieP – An Open Fieldbus Protocol
  28. Profibus
  30. RAPIEnet
  31. Honeywell SDS
  33. SERCOS interface
  34. GE SRTP
  35. Sinec H1
  36. SynqNet
  37. TTEthernet
  38. 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.

Must-read Articles ⇒

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.


You can read more articles about Electrical and you can also find books that boost your knowledge in the field of Instrumentation

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