Access To A Global Ncu Memory Area - Siemens SINUMERIK 840D sl Programming Manual

Additional functions
13.8 Link communication
Time behavior for accessing applications
The various NCU applications that access the link memory jointly at any one time must use
the link memory in a uniform way. The link memory can have different assignments for
processes that are completely separated in time.
Warning
A link variable write process is only then completed when the written information is also
available to all the other NCUs. Approximately two interpolation cycles are necessary for this
process. Local writing to the link memory is delayed by the same time for purposes of
consistency.
For more information, see
/FB2/ Function Manual Extension Functions; Multiple Operator Panels and NCUs (B3).
13.8.1

Access to a global NCU memory area

Function
Several NCUs linked via link modules can have read and write access to a global NCU
memory area via the system variables described in the following.
• Each NCU linked via a link module can use global link variables. These link variables are
• Link variables can be programmed in the same was as system variables. As a rule, the
• Applications for link variables
• Data volume comparatively small
• Very high transfer speed, therefore: Use is intended for time-critical information.
• These system variables can be accessed from the parts program and from synchronized
When a value is written in a global system variable, it can be read by all the NCUs
connected after one interpolation cycle.
13-42
addressed in the same way by all connected NCUs.
machine manufacturer defines and documents the meaning of these variables.
actions. The size of the memory area for global NCU system variables configurable.
Programming Manual, 03/2006 Edition, 6FC5398-2BP10-1BA0
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