S7-400 cycle and response times
19.2 Calculating the cycle time
S7-400H
358
System Manual, 03/2012, A5E00267695-11
19.2
Calculating the cycle time
Extending the cycle time
The cycle time of a user program is extended by the factors outlined below:
●
Time-based interrupt processing
●
Hardware interrupt processing (see also section Interrupt response time (Page 379))
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Diagnostics and error processing (see also section Example of calculation of the interrupt
●
Communication via MPI or the integrated PROFINET interface and CPs connected by
means of the communication bus
(e.g.: Ethernet, Profibus, DP) as a factor in communication load
●
Special functions such as operator control and monitoring of tags
or the block status
●
Transfer and deletion of blocks, compressing of the user program memory
●
Runtime of signals using the synchronization cable
Influencing factors
The table below shows the factors influencing the cycle time.
Table 19- 2 Factors influencing cycle time
Factors
Remark
Transfer time for the process
output image (POI) and process
input image (PII)
See tables from 19-3 onwards
User program execution time
This value is calculated based on the execution times of the
various statements (see the
S7-400 statement list
).
Operating system execution time
at the cycle control point
See Table 19-7
Extension of cycle time due to
communication load
You configure the maximum permitted communication load on
the cycle as a percentage in STEP 7 (
Programming with STEP 7
manual). See section Communication load (Page 366).
Load on cycle times due to
interrupts
Interrupt requests can always stop user program execution. See
Table 19-8
