PROFINET is a real-time Ethernet standard for the high-speed, deterministic communications required for a wide range of industrial applications including factory automation, process automation, and building automation.

PROFINET standard defines four conformance classes that build upon one another and are oriented to serve different applications and use-cases:

• Conformance Class A (CC-A): can be implemented with standard Ethernet hardware and supports basic PROFINET functions such as cyclic Real-Time (RT) communication with update times between 1ms to 512ms.
• Conformance Class B (CC-B): extends CC-A with network diagnostics via SNMP, system redundancy and network redundancy through Media Redundancy Protocol (MRP).
• Conformance Class C (CC-C): extends CC-B with the support of cyclic Isochronous Real-Time (IRT) communication with update times less than 250μs.
• Conformance Class D (CC-D): this is the most advanced PROFINET class. It utilizes Time-Sensitive Networking (TSN) capabilities such as Time-Aware Shaper (TAS) and frame preemption to achieve very high determinism and low latency.

PROFINET standard defines three types of devices: IO Controller, IO-Device and IO-Supervisor. An example of a simplified network architecture inside a factory plant is provided in Figure 3-4.

The PROFINET device implementation integrated on Sitara processors (Figure 3-5) has three major software components. The first is microcode that implements Layer 2 functionality in the device's PRU-ICSS; the second is the PROFINET device stack that runs on the Arm core; and, the third is the industrial application. TI provides additional components such as the protocol adaptation layer and device drivers in the software development kits that support Sitara processors.

As shown in Figure 3-6, the PRU-ICSS integrates complete PROFINET Layer 2 functions, including CPM/PPM processing, DHT, DCP filtering, ARP filtering, cut-through switching, and error detection. Its internal shared memory provides a PROFINET register space, and combined with the PRU's deterministic real-time processing capability, verifies consistent and predictable PROFINET frame processing latency.