Siemens Simatic S7-1500 Function Manual page 45

Cyclic program execution
3.4 Response time for cyclic and time-driven program execution
Update time of the backplane bus for ET 200SP CPUs
The following table shows the central (typical) update times of the backplane bus for the
ET 200SP CPUs.
Table 3- 6 Update time of the ET 200SP CPUs
1510SP(F)-1 PN
Update time for 250 μs to 1 ms, depending on number and type of central I/O modules
central I/O
The duration of the update time depends on the number of the I/O modules and their type (ST, HF, HS). The update
1
time is set at 1 ms for a max. central I/O configuration with standard I/O modules. You can reduce the update time down
to 250 μs, for example, by using HF I/O modules and by reducing the number of modules.
The table below is an orientation guide. It shows the approximate relationship between the
number of ET 200SP I/O modules and the bus cycle that is used. As an example, 8 bytes of
I/O data per I/O module are assumed in the table.
Number of ET 200SP I/O modules
8
16
24
32
40
48
56
64
For I/O modules with more than 32 bytes of I/O data, the bus cycle is calculated with an I/O
module of 32 bytes. In this case the I/O module requires multiple bus cycles to update its I/O
data.
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Update time of the CPU
1512SP(F)-1 PN
Input data (bytes) Output data (bytes)
64
128
192
256
320
384
448
512
ET 200SP
1515SP(F)-PC
1
64
128
192
256
320
384
448
512
Function Manual, 10/2018, A5E03461504-AD
Used bus cycle (μs)
250
250
281.25
312.5
343.75
375
406.25
437.5
Cycle and response times