Siemens Simatic S7-300 Specifications download pdf (Page 82)

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S7-300 Automation System CPU Specifications: CPU 31xC and CPU 31x

5-22 A5E00105475-03

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You have configured an S7shy300 and equipped it with following modules in two

racks:

• a CPU 314C-2

Configuring the cycle load as a result of communication: 40 %

• 4 digital input modules SM 321; DI 32 x 24 VDC (4 bytes each in the PI)

• 3 digital output modules SM 322; DO 16 x 24 VDC/0.5 A (2 bytes each in the

PI)

• 2 analog input modules SM 331; AI 8 x 12-bit (not in the PI)

• 2 analog output modules SM 332; AO 4 x 12-bit (not in the PI)

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According to the instruction list, the user program runtime is 10.0 ms.

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In this example, the cycle time is equivalent to the sum of following times:

• User program processing time:

approx. 10 ms x CPU-specific factor 1.10 = approx. 11 ms

• Process image transfer time

Process image of inputs: 100

µs + 16 bytes x 37 µs = approx. 0.7 ms

Process image of outputs: 100

µs + 6 bytes x 37 µs = approx. 0.3 ms

• Operating system runtime at the scan cycle checkpoint:

approx. 0.5 ms

The sum of the listed times is equivalent to the cycle time:

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Under consideration of communication load:

12.5 ms * 100 / (100-40) = 20.8 ms.

Thus, under consideration of time-sharing factors, the DFWXDOF\FOHWLPHis PV.

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Siemens Simatic S7-300 Specifications Page 82