Siemens S7-300 appendix Cycle extension through component-based automation CBA, Runtimes

Cycle and reaction times 5.2 Cycle time

5.2.5Cycle time extension as a result of testing and commissioning functions

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

Function	CPU 31xC/ CPU 31x
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 mode, the complete loop is executed in every cycle. This can significantly increase cycle time.

5.2.6Cycle extension through component-based automation (CBA)

By default, the operating system of your CPU updates the PROFINET interface as well as the DP interconnections at the cycle control point. However, if you deactivated these automatic updates during configuration (e.g. to obtain improved capabilities of influencing the time behavior of the CPU), you must perform the update manually. This is done by calling SFCs 112 to 114 at the appropriate times.

Reference

Information about SFC 112 to 114 is available in the STEP 7 Online Help.

Extending the OB1 cycle time

The OB1 cycle is extended by

•Increasing the number of PROFINET interconnections,

•Increasing the number of remote partners,

•Increasing the data volume and

•Incrasing the transfer frequency

CPU 31xC and CPU 31x, Technical data	5-11
Manual, Edition 08/2004, A5E00105475-05