Siemens SINAMICS Series Operating Instructions Manual page 668

Descriptions of functions
10.37 Drive Control Chart (DCC)
10.37.2 CPU time load through DCC
Calculating the DCC blocks requires CPU time. If the CPU time becomes meager, you have
to check whether all the activated blocks are required and whether all the function blocks
used need to be computed within the same sampling time.
The CPU time load can be reduced by either deactivating blocks or assigning used blocks to
a runtime group with a longer sampling time.
A list of all of the DCC blocks available for SINAMICS DCM and the required computation
times are listed in Appendix B.
Table 10- 83 CPU time load DCC blocks left-hand CUD
Time slice
1 ms
2 ms
4 ms
6 ms
8 ms
16 ms
This information applies to a left-hand CUD without additional options. These options increase the
1)
basic load of the CUD and reduce the available CPU time for the DCC blocks. Please refer to the
"CPU time load with the SINAMICS DCM" chapter for more information about the CPU load.
In this information, an average complexity of the blocks being used is assumed. If only highly
complex or very simple blocks are computed, the stated limit shifts accordingly.
Notes
● The actual CPU time load of the CUD can be read out in r9976. Please refer to the "CPU
time load with SINAMICS DCM (Page 657)" chapter for more information about the CPU
load on the SINAMICS DCM.
● To make your own calculations, the previously illustrated CPU time loads can be taken to
be "linear". This means that:
– half as many blocks in the same time slice generate half as much CPU time load, etc.
– the same number of blocks in time slices half as fast generate half as much CPU time
Examples
1. In the 1 ms time slice, 50 blocks generate about 30% additional CPU time load. For that
reason, 50 blocks in the 2 ms time slice generate about 30% × 0.5 = 15% additional CPU
time load.
2. In the 7 ms time slice, (300 + 400) / 2 = 350 blocks generate about 30% additional CPU
time load. That means 250 blocks generate 250 / 350 × 30% = 21.5% additional CPU
time load.
666
load, etc.
Number of blocks
1)
50
100
200
300
400
800
Operating Instructions, 12/2018, A5E34763375A
CPU time load
+30%
+30%
+30%
+30%
+30%
+30%
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