Siemens SINUMERIK 840D sl Function Manual page 142

Several Operator Panels on Several NCUs, Distributed Systems (B3)
Link axes
Terminology
The following terms are important for understanding the subsequent description:
● Link axis
● Local axis
● Link communication
● Home NCU
● Interpolation
● Axis change
● Configuration of link axes
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Link axes are machine axes, which are physically connected to another NCU and whose
position is controlled from this NCU. Link axes can be assigned dynamically to channels
of another NCU. From the standpoint of a particular NCU, they are not → local axes.
Dynamic changes in the assignment to a channel (exception: channel on another NCU)
are implemented based on the concept of axis container described under "Axis
container".
Axis exchange with GET and RELEASE from the part program is only available for link
axes within an NCU. In order to cross the NCU limit, the axis must first be placed in the
NCU or a channel using the axis container function so that it can then be exchanged
optionally in the same way as any other axis.
A local axis is only addressed by the NCU to whose drive bus it is connected.
The link communication is implemented by link modules on the NCUs involved. The link
communication consists of setpoints, actual values, alarm handling, global variables
(data) and signals (axis signals, PLC signals).
The NCU which sets up the drive bus connection for a → link axis and which performs
position control is referred to as the home NCU.
In the diagram "Overview of link axes", NCU2 is the home NCU for → link axis B1.
The link axis option enables interpolation between → local axes and axes on other NCUs
for NCUs with → link communication..
If the interpolation is not only local, cyclical data exchange (setpoints, actual values, ...)
takes place within an interpolation cycle. This results in dead time, in particular when
waiting for external events.
Use of a → link axis by a specific NCU can change dynamically. The axis container
mechanism described under "Axis container" is provided for this purpose. The part
program command GET is not available for link axes, and the part program command
GETD is only available on the same NCU.
With software version 4 it was only possible to exchange axes between different channels
of the same NCU.
NCUs that want to use → link axes must configure the NCU identifiers for the home NCU
of the link axis in addition to the usual channel and axis machine data.
Function Manual, 03/2009, 6FC5397-1BP10-4BA0
Extended Functions