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

2.6 Media Access Controller (MAC)

The media access control (MAC) is responsible for managing protocol access to the physical network medium. The main functions consist of:

  • Addressing: Each device on the Ethernet network has a unique MAC address, a 48-bit identifier used to distinguish devices on a network. The MAC makes sure that data packets are delivered to the correct device.
  • Frame Delimiting: The MAC sublayer defines the frame structure used for data transmission. An Ethernet frame includes a preamble, destination MAC address, source MAC address, type/length field, data payload and frame check sequence (FCS).
  • Media Access Control: The MAC sublayer controls how devices access the shared communication medium. Industrial Ethernet MAC derive here from standard Ethernet MAC, and even implement specific operation modes like on-the-fly processing and cut-though data processing. Those methods are explained later in this section.
  • Error Detection: The MAC sublayer includes mechanism for detecting errors in receive frames, typically using the Frame Check Sequence (FCS). If an error is detected, the frame is typically discarded and upper layer is getting notified.
  • Frame Transmission and Reception: The MAC sublayer handles the actual transmission and reception of frames over the network medium (layer 1). This makes sure that frames are properly formatted, addressed, and send at the correct time. Some IE protocols have different transmission phases, one phase for real-time data (process data), and second one for non-real-time data (standard Ethernet frames). This transmission phases are time multiplexed and referred to as cycle time.