Link Variables - Siemens SINUMERIK Series Function Manual

2.2.2

Link variables

Complex systems with several NCUs require for the complete system coordination of the
manufacturing processes a cyclic exchange of user-specific data between the NCUs. The
data exchange is performed via the link communication and a special memory area, the link
variables memory available for each NCU.
The size and data structure of the link variables memory can be specified for each specific
user. The data stored in the link variables memory is addressed using a special $A_DLx link
variable.
These are system-global user variables that can be read and written in part programs and
cycles by all NCUs involved in a link group if link communication has been configured. Unlike
global user variables (GUD), link variables can also be used in synchronized actions.
Figure 2-7
Requirement
The use of link axes requires a link communication defined in accordance with "Section Link
communication (Page 79)".
Link variable as NCU-global user variable
Note
If an NCU Is not a node of a link group or the link variables are not required for
communication via NCU link, the link variables can be used as the NCU-global user
variables.
Extended Functions
Function Manual, 03/2013, 6FC5397-1BP40-3BA1
Link variables
B3: Distributed systems - 840D sl only
2.2 NCU link
87