Siemens Simatic S7-300 Specifications download pdf (Page 71)

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

A5E00105475-03

5-11

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• Use the default setting wherever possible.

• Increase this value only if the CPU is used primarily for communications and if

the user program is not time critical.

• In all other situations you should only reduce this value.

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The runtimes of the testing and commissioning functions are operating system

runtimes, so they are the same for every CPU. Initially, there is no difference

between process mode and testing mode.

How the cycle time is extended as a result of active testing and commissioning

functions is shown in the table below.

Table 5-9 Cycle time extension as a result of testing and commissioning functions

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Status variable 50 µs for each variable

Control variable 50 µs for each variable

Status block 200 µs for each monitored line

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In SURFHVVPRGH, the maximum permitted communication load by is not only set in

"Communication load". It is also determined by "Process mode: maximum

permitted cycle time extension due to testing functions". Thus, the configured time

is monitored absolutely in process mode and data acquisition is stopped if a

timeout occurs. This is how 67(3 stops data requests in loops before a loop

ends, for example.

When running in 7HVWLQJPRGH, the complete loop is executed in every cycle. This

can significantly increase cycle time.

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Siemens Simatic S7-300 Specifications Page 71