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Supplementary information
16.15 Cycle and response times of the CPU 410-5H
16.15.2
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 Chapter Interrupt response time (Page 288))
● Diagnostics and error processing (see also Chapter Example of calculation of the
interrupt response time (Page 290))
● Communication via the integrated PROFINET IO 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 monitoring and modifying variables
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 16- 10 Factors influencing cycle time
Factors
Transfer time for the process
output image (POI) and process
input image (PII)
User program execution time
Operating system execution time
at the cycle control point
Extension of cycle time due to
communication load
Load on cycle times due to
interrupts
Process image update
The table below shows the time a CPU requires to update the process image (process
image transfer time). The specified times only represent "ideal values", and may be
extended accordingly by any interrupts or communication of the CPU.
274
Remark
See tables from 19-3 onwards
This value is calculated based on the execution times of the
various statements (see the
See Table 19-7
You configure the maximum permitted communication load on
the cycle as a percentage in STEP 7 (Manual
STEP 7
). See Chapter Communication load (Page 277).
Interrupt requests can always stop user program execution. See
Table 19-8
CPU 410-5H Process Automation/CPU 410 SMART
S7-400 statement list
).
Programming with
System Manual, 10/2013, A5E32631667-AA
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