Siemens SINAMICS DCM Operating Instructions Manual page 628

Descriptions of functions
10.34 Free function blocks
CPU time load through free function blocks with the SINAMICS DCM
Processing free function blocks requires considerable computation time. If little CPU time
remains, you have to check whether all the activated function modules 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 function modules or assigning
used function blocks to a runtime group with a longer sampling time.
Table 10- 82 CPU time load through free function blocks with the SINAMICS DCM
Time slice
16 ms
8 ms
5 ms
4 ms
2 ms
Notes regarding the CPU time
● The actual CPU time load of the CUD can be read out on r9976. Please refer to the
Chapter "CPU time load with SINAMICS DCM (Page 621)" for more information about the
CPU load on the SINAMICS DCM.
● To make your own calculations, the 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
● Each individual free function block can be assigned to a runtime group via parameter
(e.g. p20032). Ten runtime groups are available. Every runtime group can be assigned a
time slice using p20000.
– The time slices that can be selected with p20000 = 1 to 1096 are calculated
– The time slice that can be selected with p20000 = 9003 is that time slice, in which the
626
Number of free function blocks
52
23
12
6
3
load, etc.
asynchronously to the closed-loop control functions.
setpoint channel (function diagrams 3105 to 3155) is calculated. One of the free
function blocks assigned to this time slice is immediately calculated before the
functions of the setpoint channel.
CPU time load
+30%
+30%
+30%
+30%
+30%
SINAMICS DCM Control Module
Operating Instructions, 12/2018, A5E34888669A