Examples Of Calculating The Cycle And Response Times - Siemens SIMATIC CPU 410 System Manual

Supplementary information
18.16 CPU 410 cycle and reaction times
The result is an approximated actual cycle time. Note down the result.
Table 18- 18 Example of calculating the response time
Shortest response time
3. Next, calculate the delays in the inputs and
outputs and, if applicable, the cycle times on the
PROFIBUS DP network.
4. The result you obtain is the shortest response
time.
18.16.6

Examples of calculating the cycle and response times

Example I
You have installed an S7-400 with the following modules in the central controller:
● a CPU 410–5H in redundant mode
● 2 digital input modules SM 421; DI 32xDC 24 V (each with 4 bytes in the PI)
● 2 digital output modules SM 422; DO 32xDC 24 V/0.5 (each with 4 bytes in the PI)
User program
According to the instruction list, the user program runtime is 15 ms.
Calculating the cycle time
The cycle time for the example results from the following times:
● As the CPU-specific factor is 1.2, the user program execution time is:
● Process image transfer time (4 double-word accesses)
● OS execution time at the scan cycle checkpoint:
The total of the listed times is equivalent to the cycle time:
Cycle time = 18.0 ms + 0.109 ms + 0.31 ms = 18.419 ms.
370
approx. 18.0 ms
Process image: 9 µs + 4 ×25 µs = approx. 0.109 ms
approx. 0.31 ms
Longest response time
3. Multiply the actual cycle time by factor 2.
4. Next, calculate the delays in the inputs and
outputs and the DP cycle times on the
PROFIBUS DP network.
5. The result you obtain is the longest response
time.
CPU 410 Process Automation/CPU 410 SMART
System Manual, 05/2017, A5E31622160-AC