Modicon Quantum Automation Platform Page 5-16 Communication

5/16 Modicon Quantum automation platform Ethernet Modbus/TCP network Performance Selecting the communication architecture When selecting an architecture, take performance into account at the earliest possible stage. To do this, the developer must: 1 Know exactly what he needs: v quantity and type of devices to be interconnected v volume and type of exchanges v expected response times v environment 2 Compare his needs with the characteristics of the offers available and be aware that the actual performance level between any 2 points in an architecture depends on the weakest link in the chain, which can be: v dependent on the hardware v but also dependent on the applications (size, architecture, operating system, machine power rating, etc) which are often only vaguely defined at this stage of the project 3 Work out from these which is the most suitable architecture The purpose of the next few pages is to provide the main information and instructions needed to answer the second point. Given that the performance of an Ethernet architecture is linked to several parameters, these pages do not supply all the information needed to calculate the network performance. Their aim is to focus on the following main aspects: b Guidelines for calculating the network load so as to design an Ethernet network that meets the application requirements b Application response time to be obtained depending on the configuration used (see pages 5/17 to 5/19) b Processing capability of Modicon M340, Modicon M580, Modicon Premium and Modicon Quantum platforms so as to be able to select the CPU and define the number of Ethernet connections required on the PLC depending on the application (see pages 5/20 and 5/21) Calculating the network load Introduction When calculating the load on an Ethernet network, all the communication services of all the peripheral devices connected to the network need to be calculated. Because of the outstanding performance of the Ethernet network, the load is often less than the Ethernet network limits and does not significantly affect the application response time. This phenomenon is explained by the high speed of the Ethernet network: the network transaction time is 10% less than the application response time. In order to ensure a low network load and avoid large theoretical calculations, it is highly advisable to separate the collision domain so as to limit the network load, using only the switched network (tree, star or daisy-chain topology). Performance 2 1 3 4 5 6 7 8 9 10 2 1 3 4 5 6 7 8 9 10

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