Siemens SINUMERIK 840D sl Function Manual

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Several Operator Panels on Several NCUs, Distributed Systems (B3)Link axesExtended Functions142 Function Manual, 03/2009, 6FC5397-1BP10-4BA0TerminologyThe following terms are important for understanding the subsequent description:● Link axisLink axes are machine axes, which are physically connected to another NCU and whoseposition is controlled from this NCU. Link axes can be assigned dynamically to channelsof 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 "Axiscontainer".Axis exchange with GET and RELEASE from the part program is only available for linkaxes within an NCU. In order to cross the NCU limit, the axis must first be placed in theNCU or a channel using the axis container function so that it can then be exchangedoptionally in the same way as any other axis.● Local axisA local axis is only addressed by the NCU to whose drive bus it is connected.● Link communicationThe link communication is implemented by link modules on the NCUs involved. The linkcommunication consists of setpoints, actual values, alarm handling, global variables(data) and signals (axis signals, PLC signals).● Home NCUThe NCU which sets up the drive bus connection for a → link axis and which performsposition control is referred to as the home NCU.In the diagram "Overview of link axes", NCU2 is the home NCU for → link axis B1.● InterpolationThe link axis option enables interpolation between → local axes and axes on other NCUsfor 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 whenwaiting for external events.● Axis changeUse of a → link axis by a specific NCU can change dynamically. The axis containermechanism described under "Axis container" is provided for this purpose. The partprogram command GET is not available for link axes, and the part program commandGETD is only available on the same NCU.With software version 4 it was only possible to exchange axes between different channelsof the same NCU.● Configuration of link axesNCUs that want to use → link axes must configure the NCU identifiers for the home NCUof the link axis in addition to the usual channel and axis machine data.