Cross-Ncu User Communication, Link Variables; Link Variables - Siemens SINUMERIK 840D sl Function Manual

2.8

Cross-NCU user communication, link variables

Introduction
With large machine tools, rotary indexing machines and multi-spindle machines whose
motion sequences are controlled by more than one NCU the applications on a single NCU
must be able to exchange information rapidly with the other NCUs connected via link
module.
For this purpose there are:
● Link variables
2.8.1

Link variables

Definition
Link variables are system-global data that can be addressed by the connected NCUs as
system variables if link communication is configured. The
● contents of these variables
● their data type
● their use
● their position (access index) in the link memory
are defined by the user (in this case, normally the machine manufacturer).
Requirements
● For activation of NCU link communication, this machine data must be set:
● The link grouping must be installed and configured as described in "Configuration of a link
Application
Because link variables are system variables from a formal point of view, when they occur in
part programs and in
synchronized actions
they can usually be addressed in read/write mode.
The access options for the individual link options are also specified in 7.14.2.
Note
On installations without an NCU link, the link variables can also be used NCU-locally as an
additional means of cross-channel communication.
Extended Functions
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
Several Operator Panels on Several NCUs, Distributed Systems (B3)
MD18780 $MN_MM_NCU_LINK_MASK
grouping".
2.8 Cross-NCU user communication, link variables
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