SLAAEM2 October   2024 AM2434

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Real-Time Communication in Factories
    2. 1.2 Industrial Protocols
    3. 1.3 Serial and Ethernet-Based Communication Protocols
  5. 2Industrial Protocols
    1. 2.1 Ethernet-Based Communication Protocols
    2. 2.2 Network Topologies
    3. 2.3 OSI Layer Model
    4. 2.4 Industrial Ethernet System Block diagram
      1. 2.4.1 Two-Port Device
      2. 2.4.2 One-Port Controller
    5. 2.5 Ethernet Physical Layer (PHY)
    6. 2.6 Media Access Controller (MAC)
      1. 2.6.1 Device MAC
      2. 2.6.2 Controller MAC
    7. 2.7 Industrial Protocol Stacks
    8. 2.8 Industrial Communication Software Development Kit (SDK)
    9. 2.9 EtherCAT Device Example Using the AM243x Processor
  6. 3Conclusion

2.3 OSI Layer Model

The Open System Interconnection (OSI) layer model provides a conceptual framework that standardizes the functions of a communication system into seven distinct layers, facilitating interoperability and communication between different systems and technologies. Each layer serves a specific function and interacts with the layers directly above and below one layer, providing a structured and modular approach to the network communication.

The seven OSI layers are:

  • Physical Layer
  • Data Link Layer
  • Network Layer
  • Transport Layer
  • Session Layer
  • Presentation Layer
  • Application Layer

In industrial Ethernet systems, the OSI model is used to standardize communication protocols and makes sure compatibility and interoperability among devices. Industrial Ethernet protocols, for example PROFINET, utilizes various OSI layers, particularly the physical layer for hardware connections, the data link layer for Ethernet frame communication, and the network layer for protocol specific addressing and routing.

OSI Layer Figure 2-3 OSI Layer

The Physical Layer is handled by the Ethernet PHY. Depending on the protocol either a 10/100Mbit Ethernet PHY is used, or a 10/100/1000Mbit Ethernet PHY. New market trends also ask for single pair Ethernet (SPE) PHY, which also support speeds from 10Mbit/sec to 1000Mbit/sec.

The Data Link Layer is hosting the media access controller (MAC) implementation. Commonly used is here the standard Ethernet MAC for TCP/IP data communication. Industrial Ethernet protocols have some extensions to the MAC layer to support cyclic data exchange with high priority Ethernet frames and specific Ethernet frame handling like cut-through and on-the-fly.

Network and Transport Layer handle the Internet Protocol (IP) and UDP/TCP in Ethernet communication. Industrial Ethernet protocols can also use those three blocks, but more often the stack in Layer 5 of the industrial Ethernet protocol has direct Layer 2 access, and bypassing UDP/TCP and IP block.

The Session Layer runs the industrial Ethernet protocols stack, which is very specific to the industrial protocol.

The Presentation and Session Layer contain the industrial application, which is depends on the customer use case for the device.