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Real-Time, Determinism and Ethernet

Real-Time, Determinism and Ethernet. REALTIME Build up - test it - check it. Agenda. Definitions Real-Time Determinism Control Network Ethernet Evolution Bandwidth Switches Fast Ethernet Full Duplex Prioritisation Redundancy Real-Time / Determinism with Ethernet Mathematical Example.

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Real-Time, Determinism and Ethernet

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  1. Real-Time, Determinism and Ethernet

  2. REALTIMEBuild up - test it - check it

  3. Agenda • Definitions • Real-Time • Determinism • Control Network • Ethernet Evolution • Bandwidth • Switches • Fast Ethernet • Full Duplex • Prioritisation • Redundancy • Real-Time / Determinism with Ethernet • Mathematical Example

  4. Definitions

  5. Definitions – Real-Time • Adjective :(computer science) of a system, in which data-processing occurs as the data is generated. • Real-time systems are systems that respond to an input immediately. • Any system which uses some kind of shared transmission medium cannot be a real-time system under this definition.

  6. Definitions - Determinism • Determinism. • The ability for a system to respond with a consistent, predictable time delay between input and response. • This time delay is commonly referred to as a scan time and is usually given a maximum value.

  7. Definitions – Control Network • That network which links the controllers of a process to the devices which the process controls. May also link several controllers to one (or more) master controllers. • Merges with the automation network and the device network. Information Automation Control Device

  8. Ethernet Evolution

  9. Ethernet Evolution - The ALOHA network • Pioneered the concept of a shared transmission channel, or the CSMA/CD model. • Developed to link the IBM 360 mainframe to the other islands of Hawaii

  10. Ethernet Evolution - The First Ethernet • Designed by Bob Metcalf at PARC in 1972/3

  11. Ethernet Evolution • Ethernet today is not the same as it was when it was invented 30 years ago. • Improvements have consisted of : • Higher bandwidth • Dual duplex communication • Switching • Prioritisation • VLANs

  12. Ethernet Evolution - Bandwidth

  13. Ethernet Evolution – Half, Full and Dual Duplex • Half duplex – one pair of cables used for communication. • Can either be for transmission or reception, but not both at the same time. • Full duplex – two pairs of cables used for communication. • One pair for transmission, one for reception. • Dual duplex – one pair of cables used for communication. • The pair can be used for transmission and reception at the same time.

  14. Collision Ethernet Evolution - Switching • Original Ethernet composed of one collision domain. • Only one device at a time can talk.

  15. TX TX F1 F2 F3 F4 F5 F6 F8 F9 F1 F7 Ethernet Evolution - Switching • Switched Ethernet has broken up the collision domains • Now lots of little collision domains. • Still only half duplex. Collision

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