Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 User Manual
Page 95
Cycle and reaction times
5.2 Cycle time
CPU 31xC and CPU 31x, Technical data
Manual, Edition 08/2004, A5E00105475-05
5-13
Additional marginal conditions
The maximum cycle load through communication in the measurement is 20 %.
The lower graphic shows that the OB1 cycle is influenced by increasing the cyclical
PROFINET interconnections to remote partners at PROFINET:
0
32
64
96
128
160
200
0
2
4
6
8
10
12
14
Cycle time in ms
Dependency of the OB1 cycle on the number of interconnections
Number of interconnections
OB1 cycle with 32 remote
PROFINET partners
OB1 cycle with 5 remote
PROFINET partners
Base load through PROFIBUS devices
The 16 PROFIBUS devices with their interconnections among each other generate an
additional base load of up to 1,0 ms.
Tips and notes
The upper graphic already includes the use of uniform values for the transfer frequency of all
interconnections to a partner.
•
The performance can drop by up to 50 % if the values are distributed to different
frequency levels.
•
The use of data structures and arrays in an interconnection instead of many single
interconnections with simple data structures increases the performance.