In this article, we discuss about various communication protocols used in PLCs. We know that we, people, communicate with others with the help of languages. Without the help of language, it is very hard and difficult to convey our messages to others. In this way, different automation devices are communicating with each other instruments by using standard communication protocols.
What is a Communication Protocol?
A protocol means it is a set of rules for communication (sends and receives data) among network devices. The communication protocol serves as a means for devices to connect and communicate with one another. Without a communication protocol, devices are only connected to each other but cannot communicate with one another. So we could say that PLC communication protocols are the communication protocols that a PLC uses to communicate with various field devices, programming devices, other PLCs, HMIs, controllers, SCADA, etc.
List of Communication Protocols:
• AS-i – Actuator-sensor interface
• BSAP – Bristol Standard Asynchronous Protocol
• CC-Link Industrial Networks
• CIP (Common Industrial Protocol)
• Ethernet Global Data (EGD)
• Ethernet Powerlink
• FOUNDATION Fieldbus – H1 & HSE
• HART Protocol
• HostLink Protocol
• 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
• PieP – An Open Fieldbus Protocol
• Honeywell SDS
• SERCOS III
• SERCOS interface
• GE SRTP
• Sinec H1
• MPI – Multi-Point Interface
AS-i – Actuator-sensor interface
Actuator-Sensor Interface is an intelligent cabling system that is designed to replace the discrete wires linking actuators and sensors with a Programmable Logic Controller or other controlling devices.
BSAP – Bristol Standard Asynchronous Protocol
This protocol is developed by Bristol Babcock and it was managed by Emerson. This is a master-slave protocol suited to both asynchronous low-speed wide area networks and synchronous high-speed local networks.
CC-Link Industrial Networks This is a group of open industrial networks that enables devices from various manufacturers to communicate. It is used in various industrial automation applications at the machine, line levels, and cell.
CIP (Common Industrial Protocol)
This protocol is supported by Open DeviceNet Vendors Association (ODVA), an organization that supports network technologies based upon CIP such as DeviceNet, EtherNet/IP, CIP Safety, and CIP Sync.
It is a scheduled communication protocol designed for cyclic data exchange.
It is an application-level protocol used in the automation industry. It is a communication tool that allows you to logically communicate between a PLC and money control devices such as conveyors, motors, level sensors, etc.
It is an asynchronous byte-oriented protocol that is used to communicate with only the Rosewell devices based on RS-232.
DNP stands for Distributed network protocol. It is a set of communication protocols used between components in process automation systems.
This protocol is used by DirectLOGIC PLCs and is used in APS vacuum controls since 1999. It is also a master-slave protocol by using RS-232 or RS-422 physical layers with a baud rate from 300 to 38,400
EtherCAT stands for Ethernet for Control Automation Technology. It is an Ethernet-based Fieldbus system. This is protocol is standardized in IEC 61158 and it is suitable for both soft and hard real-time computer equipment in the automation industry.
Ethernet Global Data (EGD)
It is a protocol that enables the producer to share a portion of its memory to all the connected devices at a scheduled periodic time. It is developed for GE Fanuc PLCs to communicate data between PLCs, HMI, SCADA.
It is an open application layer protocol. It is useful for in-home and commercial purposes only. It is not designed to run in industrial applications. It is an advanced version of standard Ethernet. This protocol was developed by Rockwell Automation
It is a real-time protocol for standard Ethernet. It is an open protocol managed by the Ethernet PowerLink Standardization Group called EPSG.
FOUNDATION Fieldbus – H1 & HSE
It is a type of FOUNDATION Fieldbus protocol version. Foundation H1 is a bi-directional communication protocol used for make communication between field devices and control systems.
Factory Interface Network Service is a protocol used by Omron PLCs, over different physical networks such as Ethernet, DeviceNet, RS-232, Controller link.
It is a hybrid analog+digital protocol. The main advantage of HART Protocol is that it can communicate over 4-20 mA analog instrument current loops, sharing the pair of wires. It stands for Highway Addressable Remote Transducer Protocol
This protocol is developed based on ASCII protocol which is usually used for communication over RS232 or RS422.
It is a serial bus system that works on RS-232 and RS-485. This protocol was developed by Phoenix Contact.
It is an open protocol used for industrial automation, originally developed by Yaskawa and presently maintained by Mechatrolink Members Association (MMA)
It is a peer-to-peer protocol that runs at 1 mbs. This protocol specifies both software and hardware layer.
This protocol is based upon ASCII protocol which consists of command and response messages containing data from the Optomux unit.
OSGP – The Open Smart Grid Protocol
OSGP is a family of specifications published by the European Telecommunication standards institute used in control networking standards for smart grid applications.
PieP – An Open Fieldbus Protocol
PieP stands for Process Image Exchange Protocol. It is a very simple Fieldbus protocol used for process automation. This is an application layer protocol that was developed by TCP/IP. PieP employs a method of transferring process images between I/O Devices and the PLC, which simplifies the protocol’s use.
It is a standard for Fieldbus communication in automation technology and developed by SIEMENS Automation
It is an industry technical standard for data communication over industrial Ethernet, which is designed for collecting data.
It stands for Real-time Automation Protocols for Industrial Ethernet.
Honeywell Smart Distributed System protocol was developed by Honeywell and it is supported by Holjeron. SDS is an open event-driven protocol used over Controller area network-based industrial networks.
The Sercos (serial real-time communication system) interface is a globally standardized open digital interface for the communication between industrial controls, motion devices (drives) and input-output devices (I/O)
This protocol is based on IEE802.3. It implements synchronous duplex data transmission using 100BaseT physics and was developed as a proprietary system by Motion Engineering Inc.
Time-Triggered Ethernet is a scalable networking technology that uses time scheduling to deliver deterministic real-time communication over Ethernet.
MPI – Multi-Point Interface
This protocol is developed by Siemens. This is used for connecting the stations programming, operator consoles, and other devices in the SIMATIC family.