Siemens SINUMERIK Series Function Manual page 109

Drive distribution and communications utilization
In a system with several NCUs that in conjunction with axis containers alternately traverse
axes of another NCU (link axes), the distribution of the drives connected to the NCU decides
the utilization of the link communication.
● Symmetric drive distribution
● Asymmetric drive distribution
Extended Functions
Function Manual, 03/2013, 6FC5397-1BP40-3BA1
In the case of a symmetric drive distribution, the drives addressed via the axis container
are connected to both NCUs. On account of this arrangement, the maximum possible
number of drives can still be addressed via the logical machine axes images (LAI) on
both NCUs.
Figure 2-16 Symmetric drive distribution
In the case of an asymmetric drive distribution, the drives addressed via the axis
container are only connected to NCU1. On account of this arrangement, the maximum
possible number of drives can only be addressed via the logical machine axes images
(LAI) on NCU2. Only the maximum number minus the drives used by NCU2 can be
addressed via the LAI of NCU1. In order to also be able to use the maximum number of
drives on NCU1, they must be connected to NCU2 and addressed from NCU1 via the
NCU link. This results in a higher cyclic link communication load.
Figure 2-17 Asymmetric drive distribution
B3: Distributed systems - 840D sl only
2.2 NCU link
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