In modern industrial automation processes, mechanical equipment and environmental monitoring devices of various sizes are no longer considered as isolated components. Devices such as circuit breakers, energy meters, protection relays, sensors, and PLCs have gradually evolved into intelligent systems capable of transmitting data, reporting operational status, and even receiving control commands.
All of this information becomes visible through SCADA or DCS software platforms. However, the key question is how do these diverse industrial devices communicate with each other so seamlessly?
The answer lies in industrial communication protocols.
Why Are Industrial Communication Protocols Essential?
Industrial communication protocols serve as a common language between industrial devices. Without them, even the most advanced equipment wouldn’t be able to operate together within an integrated, secure, and efficient industrial network.
For this reason, understanding industrial communication protocols is essential for:
- Electrical and automation engineers
- Industrial IoT (IIoT) specialists
- System integrators
- Technical and maintenance managers
What Is an Industrial Communication Protocol?
An industrial communication protocol is a set of standardized rules and procedures that define:
- How data is formatted
- How information is transmitted and received
- How devices identify and recognize each other
- How communication errors are detected and handled
A Simple Example
Just as two humans must speak the same language to understand each other, two industrial devices must support a common protocol to exchange data.
For example, a PLC cannot read data from an energy meter unless both devices support protocols such as Modbus, PROFINET, or EtherNet/IP.
From Proprietary Protocols to Open Standards
Early Days of Industrial Automation
In the early stages of industrial automation most communication protocols were proprietary. Each manufacturer developed its own protocol, which led to several challenges:
- Strong dependency on a single vendor
- High development and maintenance costs
- Limited scalability and system upgrades
The Birth of Modbus and the Communication Revolution
In 1979, the introduction of Modbus as the first open industrial communication protocol marked a major turning point. Modbus enabled devices from different manufacturers to communicate using a common addressing structure.
Today, open and standardized protocols have become global industry standards.
Difference Between Protocols and Physical Media
To better understand industrial data transmission, it is important to distinguish between the communication protocol and the physical media.
Protocol (The Vehicle)
The protocol defines the data structure, encoding method, and communication behavior of devices.
Examples include:
Physical Media (The Road)
The physical madia is the actual path through which data travels:
- RS-485 cables
- Ethernet cables
- Fiber optic cables
- Wireless communication
This media acts as the road for data transmission. In some cases, a single protocol can operate over different physical media, such as Modbus RTU over RS-485 and Modbus TCP over Ethernet.
What Are Fieldbus Protocols?
Fieldbus protocols are among the oldest and most reliable industrial communication technologies. They typically use serial communication and transmit data bit-by-bit through a bus topology.
Key Features of Fieldbus Protocols
- Use of RS-485 cabling
- Support for long cable distances
- High reliability in harsh industrial environments
- Strong resistance to electrical noise
- Daisy-chain topology
- Guaranteed data transmission order
Popular Fieldbus Protocols
Modbus RTU
- One of the simplest and most widely used industrial protocols
- Master/Slave architecture
- Ideal for sensors, energy meters, and simple industrial devices
With years of experience in research, development, and production of Industrial IoT (IoT) devices, environmental monitoring systems, communication gateways, and industrial SCADA software, Sepehr Informatics Derakhshan implements Modbus RTU in a highly reliable, optimized, and fully industrial-grade manner.
Profibus
- Extremely popular in Europe
- Faster and more advanced than Modbus
- Suitable for industrial production lines
- Advanced handshake mechanisms
- Built-in diagnostic capabilities
CAN bus
- Highly fault-tolerant
- Designed specifically for automation
- Widely used in automotive and industrial machinery
- Enhances industrial automation reliability
Industrial Ethernet Communication Protocols
As industrial systems demand higher data speeds and increased data volumes, Ethernet-based industrial protocols have become a fundamental standard. Unlike Fieldbus protocols, Ethernet transmits data in frames and packets, enabling real-time, high-speed communication.
Key Features of Industrial Ethernet
- Very high data transmission speed
- Use of network switches
- Efficient handling of large data volumes
- Support for fiber optics and RJ45 cabling
- Full-duplex data transmission
- Ideal for large-scale SCADA and monitoring systems
Key Industrial Ethernet Protocols
Modbus TCP/IP
- Network-based version of Modbus
- Ideal for remote monitoring and SCADA systems
- Simultaneous data acquisition from multiple devices
EtherNet/IP
- Widely used in North America
- Based on standard Ethernet and TCP/UDP protocols
- Highly flexible
- Popular in PLC-based automation systems
PROFINET
- Advanced evolution of Profibus
- High-speed communication
- Solves synchronization and real-time timing challenges
- Ideal for high-precision manufacturing environments
Wireless Communication and the DNP3 Protocol
Wireless communication is commonly used for monitoring and data acquisition. However, DNP3 is specifically designed for power utilities and critical infrastructure, providing reliable long-distance communication.
In most industrial projects, multiple protocols are used simultaneously. Typically:
- Modbus RTU is used at the device level
- PROFINET or EtherNet/IP at the control level
- SCADA systems at the monitoring level
In such architectures, gateways act as translators, enabling seamless communication between different protocols.
Cybersecurity in Industrial Networks
Serial communication networks offer higher inherent security due to limited physical access. In contrast, Ethernet-based industrial networks require robust cybersecurity measures.
To address these risks, standards such as IEC 62443 and UL 2900 have been developed to enhance the security of industrial devices and communication networks.
Choosing the Right Industrial Communication Protocol
Fieldbus protocols generally offer lower data speeds but provide simpler architectures and reduced implementation costs, making them suitable for:
- Sensors
- Energy meters
- Simple industrial devices
On the other hand, Industrial Ethernet protocols deliver significantly higher speeds and support large data volumes. Although they require more advanced network infrastructure, they are the best choice for:
- Factory-wide integration
- PLC-to-PLC communication
- SCADA and centralized monitoring systems
Conclusion
Industrial communication protocols are the foundation of industrial automation, Industrial IoT (IIoT), and smart power systems. Selecting the appropriate protocol has a direct impact on system reliability, cybersecurity, scalability, and overall performance, playing a critical role in the success of industrial projects.
