Cycle and response times
7.2 Cycle time
7.2.5 Cycle time extension as a result of testing and commissioning functions
Technology CPU runtimes
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 7-5 Cycle time extension as a result of testing and commissioning functions
Function Technology-CPU
Status variable 50 μs for each variable
Control variable 50 μs for each variable
Block status 200 μs for each monitored line
Configuration during parameter assignment
For Process Operation, the maximum permissible cycle load by communication is not
specified in "Cycle load by communication", but rather in "Maximum permitted increase of
cycle time as a result of testing functions during process operation". Thus, the configured
time is monitored absolutely in process mode and data acquisition is stopped if a timeout
occurs. This is how
STEP 7
stops data requests in loops before a loop ends, for example.
When running in
Testing Operation, the complete loop is executed in every cycle. This can
significantly increase cycle time.
S7-300 CPU Data: CPU 315T-2 DP
Manual, 12/2005, A5E00427933-02
7-9
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