PROFINET is one of the world’s leading Industrial Ethernet-based communication solutions widely used in industrial automation applications. The modifications to the Ethernet standard used by PROFINET enable deterministic communication and ensure real-time data transmission even in harsh operating conditions.
PROFINET’s protocols are built to ensure specific and tight time constraints on communications, and were developed from PROFIBUS, which is a standard for fieldbus communications that also supports automation applications. Where PROFINET differs from PROFIBUS is that PROFIBUS is based on Industrial Ethernet (IE) and extends IE with additional features that allow for higher-speed and more flexible communications better suited for communications with control automation components.
The main benefit of PROFINET deterministic communications is that it enables automation systems to operate with precise input/output (I/O) structure limits, which allow for precise calculation of the maximum update times for communications. PROFINET is used to communicate between controllers and devices using controllers such as programmable logic controllers (PLCs), distributed control systems (DLCs), and programmable automation controllers (PACs). PROFINET devices, also known as input/output (I/O) devices, include I/O blocks, RFID readers, proxies, controllers, drives, process instruments, and vision systems.
PROFINET makes use of three communication channels for data exchange, which include TCP/IP, UDP/IP, real-time (RT), and Isochronous Real-Time (IRT). PROFINIT only uses TCP/IP and UDP/IP communication channels for tasks that are not time critical, for instance configuration and parameterization. PROFINIT RT Ethernet frames are of the PROFINET EtherType:0x8892 and upon arrival at the destination node, the PROFINET RT frame is directly pointed to the PROFINET application. This mode bypasses TCP/IP layers and avoids the variable processing times typical of TCP/IP, which happens as the PROFINET RT frame is directed from Ethernet layer to PROFINET layer 7. This allows for enhanced determinism and communication speed.
With IRT data exchange, which makes use of an ultra-precise timing clock to prioritize the transmission of critical data traffic while buffering the remaining communications to ensure transmission. In the case of PROFINET IRT, the data exchanges happen within tens of microseconds to a few milliseconds, as opposed to typical real-time data exchange which experiences bus cycles times less than ten milliseconds.
An Industrial-grade protocol, such as PROFINET, is crucial for many time sensitive Industrial applications, as the standard Ethernet protocol isn’t well suited for industrial applications. PROFINET Industrial Ethernet systems are better designed for installation in extreme industrial environments, with cables and connectors that employ special features and construction to enhance their reliability to meet industrial requirements. For instance, PROFINET connectors are often equipped with more robust lock mechanisms, ruggedized cabling with additional layers and shielding, as well as more effective environmental protection measures.
PROFINET routers use IP addresses for communication, but unlike Ethernet PROFINET they use DCP protocol instead of DHCP for assigning addresses. In this way, a PROFINET network IP address can be assigned without the need for a central server. PROFINET I/O devices are controlled via a programmable logic controller (PLC) that is also known as an I/O-controller. When a PROFINET I/O device is first active on the network, the PLC transmits a DCP broadcast message, and all of the I/O devices on the subnet respond with their unique MAC addresses. Following this, the PLC sends a DCP message to each I/O Device detailing it's IP address and station name. After that is accomplished the PLC begins configuration of the I/O device with the DCE/RPC protocol that employs UDP over IP. Being IP-based, PROFINET routers are able to connect to local area networks (LANs) and combine LANs to form wide area networks (WANs) with specialized algorithms that automatically determine optimum transmission routes amongst the networks.
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