Calculating The Cycle Time; Table 16-2 Factors Influencing Cycle Time - Siemens SIMATIC S7-400H System Manual

16.2

Calculating the cycle time

Extension of the cycle time
The cycle time of a user program is extended by the factors outlined below:
● Time-based interrupt execution
● Hardware interrupt handling (see also section Interrupt reaction time (Page 281))
● Diagnostics and error processing (see also section Example of calculation of the interrupt
● Communication via MPI and CPs connected to the communication bus (e.g.: Ethernet,
● Special functions such as controlling and monitoring tags or the block status
● Download and deletion of blocks, compression of user program memory
Influencing factors
The table below shows the factors influencing the cycle time.
Table 16-2
Factors
Transfer time for the process
image of outputs (PIO) and inputs
(PII)
User program execution time
Operating system execution time
at the scan cycle checkpoint
Extension of cycle time due to
communication load
Load on cycle times due to
interrupts
S7-400H
System Manual, 09/2007, A5E00267695-03
reaction time (Page 283))
Profibus, DP) as a factor in communication load
Factors influencing cycle time
Comment
See tables from 16-3 onwards
This value is calculated based on the execution times of the
various statements (see the
See Table 16-8
You configure the maximum permitted communication load on
the cycle as a percentage in STEP 7 (
manual). See section Communication load (Page 268).
Interrupt requests can always stop user program execution.
See Table 16-9
S7-400 cycle and reaction times
16.2 Calculating the cycle time
S7-400 statement list
).
Programming with STEP 7
261