Getting Started with Deterministic Ethernet
Deterministic Ethernet is opening up new opportunities and expanding the market potential of this widely deployed networking standard. If you have an application that may benefit from Deterministic Ethernet, use the guide below to help you get started with your project.
Define your real-time requirements.
An important starting point is to understand the demands of your application in terms of its real-time requirements. The latency and jitter that can be tolerated with delivery of data packets to their destination must be understood. Many control loop applications are defined in terms of the "cycle time" for control signals. Cycle times between 1ms and 100ms will significantly benefit from using deterministic Ethernet. Cycle times below 1ms can be accomplished only with deterministic Ethernet.
Define the network topology.
Most people think of star topologies with Ethernet since that is what they are used to with enterprise networks. In a star topology, each device is wired directly to a multiport switch. But there are also line and ring topologies, where end devices are wired to each other, thus saving on wiring and switch infrastructure. Ring topologies also provide redundancy, increasing system reliability. These topologies are widely used in industrial control applications. Line and ring topologies require 2-ports with an embedded Ethernet switch at each device.
Evaluate whether a specific protocol is needed.
If your product needs to be compatible with other devices in an Industrial Control environment, it may need to support multiple industrial Ethernet protocols. If your network is being used for real-time control and is independent of other systems, you can choose to use one of the protocols or you may choose not to use such a protocol.
Select the right semiconductor and software partner.
Look for a partner who can support you during the selection and development process. There are several companies offering deterministic Ethernet components, software and modules. Be sure that your partner has the experience and range of products to meet your needs now and in the future as those needs evolve. If you are designing with a star topology, a single port Ethernet MAC device may work, although a two port device would allow for redundant connections. For line or ring topologies, or for redundancy, two port Ethernet devices are required.
Design and test your network interface.
The best way to start your evaluation is with a Starter Kit that provides a complete prototyping environment. A good reference design will enable you to drop the Ethernet interface schematic and firmware/software into your design easily and efficiently. Make sure that all software APIs are well documented and supported directly by the manufacturer. You need to get your questions and support handled quickly and efficiently. This is particularly important as you move through the testing phase where real-time deterministic poerformance requierments are put through their paces.