Industrial communication protocols are a set of established rules that aim to create seamless communication between industrial devices and systems. In recent years, many communication protocols have been developed, each dedicated to a specific purpose and environment.
These protocols are used to provide field equipment, such as wireless sensors and machines, with connectivity within and between industrial networks. Broadly speaking, industrial networks can be differentiated into four different layers:
- Physical layer
This layer consists of wireless transducers, actuators or sensors. These devices collect process or environmental control information and transmit it to control or monitoring systems. They also execute field commands, such as physically moving the rotor.
- Control layer
It consists of logic controllers, such as PLCs or distributed control systems (DCS). Its main function is to provide local control of the various devices in an industrial network.
- Supervision Layer
It includes a SCADA/HMI for a better control and supervision of the industrial activity.
Characteristics of industrial communication protocols
Each industrial communication protocol has its own verification method that covers authentication, detection, signaling, and error correction. This check is used in protocols to ensure that data received at a destination node is identical to data transmitted. Electrical noise, connection problems, or a faulty part can interfere with effective data communications.
Industrial communication protocols can communicate with networks using 3 different methods: master/slave, token ring, and Peer-To-Peer (P2P). In turn, the protocols are subdivided into proprietary and open depending on whether they have been developed by a specific manufacturer or if they have been conceived and developed by more than one organization acting collaboratively. Most open protocols have been developed through a long iterative process of proposing, consulting, and adjusting proposed standards before a standard is published.
The following are the main industrial communication protocols.
It is a communication protocol based on a master/slave or client/server architecture. The main goal of the protocol is to facilitate reliable and fast communication between automation and field devices.
Modbus allows you to connect a master device, such as a computer, with several slave devices, such as measurement and control systems.
The different Modbus data transmission modes are as follows:
- ModbusTCP. Ethernet TCP/IP communication based on a client/server model.
- Modbus RTU. Consisting of an asynchronous serial transmission through RS-232 or RS-485.
- ModbusASCII. It is similar to the previous one except that it uses a different data format and is not as widely used as the RTU.
This communication network is suitable for fast and sensitive applications as well as for complex communication tasks. Another important feature is that data is transmitted in cycles, very efficiently and quickly. However, alarms, parameters and diagnostics are transmitted only when absolutely necessary, not cyclically.
At the field level, distributed peripherals such as I/O modules, transducers, drives, valves and operation panels work in automation systems, through an efficient real-time communication system, either Profibus DP or the ProfibusPA.
- Profibus DP
It is a high speed solution. It is the result of a specific development for communication between automation systems and decentralized equipment. It is applicable in control systems where access to distributed I/O devices is emphasized. Today, around 90% of applications where Profibus is used carry Profibus DP.
- Profibus PA
Developed to cover the requirements of industrial automation where automation systems and process control systems are connected to field equipment, such as pressure and temperature transmitters, converters or positioners, among others.
It allows measurement and control through one line and two individual cables. It also powers field equipment in intrinsically safe areas. In addition, it allows maintenance and equipment connection/disconnection even during operation without interfering with other stations in zones.
Profinet is an industrial Ethernet communication protocol based on open TCP/IP and IT standards and developed with a focus on similarity to Profibus DP. It is a mechanism for exchanging data between controllers and devices.
The controllers are usually programmable logic controllers (PLC) and Distributed Control Systems (DCS), while the devices can be I/O modules, artificial vision systems, RFID system readers, proxies, or even other automatons.
In today’s automation technology, Ethernet and information technology are becoming more and more the order of the day with established standards such as TCP/IP and XML.
The industry needs more precise communication, due to high operating costs and productivity requirements. Unlike the Internet, in factories data and messages must arrive exactly when expected, so delays and errors are not acceptable.
It is an open device level network based on CAN technology. It was designed to interface field level devices such as switches, sensors, panel displays or barcode readers with higher level controllers such as PLCs. It has the capacity to support 64 nodes and 2048 devices.
It allows to reduce the cost of the network by integrating all the devices in a four-wire cable that carries both data and energy conductors. Mains power allows devices to be powered directly from the network and therefore fewer physical connection points. It is mainly used in the semiconductor and automotive industries.
It is a communication network standard capable of handling large amounts of data at speeds of 10 Mbps or 100 Mbps, and up to 1500 bytes per packet. It is a specification that uses an open protocol at the application layer.
Its industrial application is fundamentally based on control applications. It’s easy to set up, operate, maintain, and expand. It is also compatible with most Ethernet switches.
It is a technology used with personal computers, mainframes, robots, I/O devices and adapters, and PLCs, among other devices.
It is an open control network, using the Common Industrial Protocol (CIP) to combine the functionality of a P2P network and an I/O network, providing high-speed performance. It is the combination of a Data Highway Plus (DH+) and a remote I/O. It is primarily used for real-time data transfer of time-critical data.
It can keep a maximum of 99 nodes connected with a data transfer rate of five million bits per second. Provides media and communication redundancy at all network nodes.