Siemens SIMATIC PCS 7 - Page 371

Supplementary information
18.16 CPU 410 cycle and reaction times
CPU 410 Process Automation/CPU 410 SMART
System Manual, 05/2017, A5E31622160-AC
371
Calculation of the actual cycle time
● Allowance for communication load (default value: 20%):
18.419 ms * 100 / (100–20)
= 23.024 ms
.
● There is no interrupt processing.
So the actual, cycle time is approx.
23 ms
.
Calculating the longest response time
● Longest response time
23.024 ms * 2
= 46.048 ms
.
● The delay of the inputs and outputs is negligible.
● All the components are plugged into the central controller; DP cycle times do not
therefore have to be taken into account.
● There is no interrupt processing.
So the longest, rounded up response time is
= 46.1 ms
.
Example II
You have installed an S7-400 with the following modules:
● a CPU 410–5H in redundant mode
● 4 digital input modules SM 421; DI 32×DC 24 V (each with 4 bytes in the PI)
● 3 digital output modules SM 422; DO 16xDC 24 V /2 (each with 2 bytes in the PI)
● 2 analog input modules SM 431; AI 8x13 bit (not in the PI)
● 2 analog output modules SM 432; AO 8x13 bit (not in the PI)
CPU parameters
The CPU parameters were assigned as follows:
● Cycle load due to communication: 40%
User program
According to the instruction list, the user program runtime is 10.0 ms.