The definitive guide to PROFINET with IIoT

Although 4–20 mA and HART remain widely used, digital networks are increasingly gaining traction in the industrial environment because they align better with digitalization initiatives. Discussions about the continued relevance of analog systems are common, as they are robust and straightforward, making field operations easier. However, the question remains: how do we achieve transparent connectivity between the field and control systems?

Modern controllers and equipment generate significant amounts of data, which requires advanced communication protocols such as Modbus RS485, OPC, and PROFIBUS DP. Additionally, technologies like FOUNDATION Fieldbus H1, PROFIBUS PA, and PROFINET provide even greater integration capabilities. These industrial networks connect field devices with controllers, enabling diagnostics, configuration, and advanced functionality far beyond what pure analog can offer.

Despite these advancements, 4–20 mA continues to dominate in the field, largely due to the gap between vendor concepts and user realities, as well as the complexity of digital networks delaying analog’s retirement. However, the rise of IIoT and AI is accelerating digitalization, making Ethernet-based protocols and wireless communication increasingly common in new projects. The trend is clear: more digital solutions are coming, and we must be prepared to adopt them.

When installing a router or any device connected to the Internet, you have likely encountered an Ethernet cable. Many assume that “Ethernet” refers only to the cable itself; in reality, the cable represents just the physical layer of an Ethernet network.

Ethernet supports multiple communication protocols over these cables. Common examples include Internet Protocol (IP) and Transmission Control Protocol (TCP), which are widely used in everyday applications. However, industrial environments require additional protocols to meet the more complex demands.

On the plant floor, controllers must access data from drives, I/O, and workstations with rapid response times, while the network must withstand harsh conditions such as abrasion, humidity, and temperature fluctuations. To meet these demands, automation experts developed Industrial Ethernet, and from this foundation, PROFINET emerged as a robust Ethernet-based protocol for industrial applications.

PROFINET is an Ethernet-based industrial communication protocol that connects process devices - such as sensors and actuators - to control systems. It was developed by the PROFIBUS and PROFINET International (PI) organization in collaboration with multiple industry partners.

The protocol complies with the IEEE 802 Ethernet standard and is defined in IEC 61158 and IEC 61784, enabling seamless integration of diverse devices on the same network. For example, a printer and a flowmeter can coexist within a single infrastructure. Unlike typical home networks, PROFINET offers extremely fast cycle times, often in the sub-millisecond range, making it suitable for industrial automation.

To understand its structure, we refer to the ISO/OSI model, which defines seven layers for network communication. Ethernet typically uses four layers:

• Ethernet for physical and data link
• IP for network
• TCP or UDP for transport
• Other protocols for specific functions

PROFINET generally follows this model but can bypass certain layers in some applications. For instance, Real-Time (RT) PROFINET omits the network and transport layers to accelerate communication.

• TCP/IP for configuration, settings, and cyclic read/write operations
• Real-Time (RT) for automation tasks with cycle times between 1 and 10 milliseconds
• Isochronous Real-Time (IRT) for highly precise, synchronized communication using scheduled switching

This layered approach ensures flexibility, speed, and reliability, making PROFINET a cornerstone for modern industrial automation and IIoT integration.

PROFINET operates on a provider-consumer model for data exchange, replacing the traditional master-slave approach used by PROFIBUS. Devices within a PROFINET system are typically organized into three categories:

• Controller: Usually a programmable logic controller (PLC) or distributed control system (DCS) that executes the automation program. The controller sends outputs to I/O devices and receives inputs from them, similar to a Class 1 master in PROFIBUS.
• Devices: Field components such as sensors and actuators that communicate with the controller via Ethernet connections, functioning similarly to slaves in PROFIBUS.
• Supervisor: Systems such as PCs, HMIs, or diagnostic tools used for monitoring, commissioning, and troubleshooting, comparable to PROFIBUS Class 2 masters.

A PROFINET I/O system requires at least one controller and one device, but configurations can vary widely: multiple controllers for a single device, one controller for multiple devices, or even multiple controllers managing multiple devices. Supervisors are typically used temporarily during commissioning or diagnostics.

In addition to these core elements, a PROFINET network includes components such as switches and wireless access points. Some of these components can also act as I/O devices, providing enhanced diagnostic capabilities.

To configure a PROFINET I/O device, two elements are essential: a supervisory tool and a General Station Description (GSD) file. The GSD file, provided by the device vendor, is similar to those used in PROFIBUS but follows an XML-based format known as GSDML.

Once configuration is complete, the GSDML file is downloaded to the controller, establishing communication with the connected devices. From this point, cyclic data - such as inputs and outputs - flows continuously between the controller and devices, while acyclic data, including diagnostic information, is exchanged as needed.

The choice between PROFIBUS and PROFINET depends on the specific requirements of your application. PROFIBUS is a well-established digital protocol based on serial communication, while PROFINET is a modern protocol built on Industrial Ethernet. PROFINET offers significantly higher bandwidth and faster communication cycles, enabling the transfer of larger data packets.

Here you can find an overview of the differences between PROFIBUS and PROFINET:

Another advantage of PROFINET is its compatibility with wireless technologies. As an Ethernet-based standard, it can integrate with Wi-Fi or Bluetooth where appropriate, providing flexibility for mobile and remote connectivity.

Connectivity and openness are fundamental to building efficient IIoT systems. Collecting accurate field data is essential for generating actionable insights, and PROFINET provides a reliable and transparent link between field devices and IIoT ecosystems like Endress+Hauser's Netilion.

One of PROFINET’s strengths is its ability to coexist with other protocols, allowing operators to transition into the digital era without abandoning familiar infrastructure. Furthermore, data can be exported from the field to higher-level systems using open standards such as OPC UA, working alongside PROFINET to enable seamless integration with cloud databases.

PROFINET is already a key enabler of IIoT, and its role will continue to grow.