Lenze C520 - Switch-Off Behavior; Retain Variables and Persistent Variables

9.3 Switch-o behavior
The controller has internal buer capacitors to save data during the shutdown process. This
memory funcon is iniated automacally if a voltage failure is detected.
Certain circuit secons, e.g. backplane bus supply and USB, are switched o
directly in the event of voltage failure in order to maintain voltage for the
internal saving process for a constant amount of me.
9.3.1 Retain variables and persistent variables
Retain variables
The controller automacally saves retain variables in the event of voltage failure. In this way,
they remain available when operaon resumes. Retain variables are reinialized when devices
are reset or a new PLC program is downloaded. The values are preserved in the event of an
online change.
Example
The values of a drive system which can no longer be read out from the machine due to a
voltage failure should be persistent. These values should also be persistent if the
corresponding value only changes through the inuence of the PLC.
Variable Use case Storage
Thermal sensor Changes, requires a sensor system. Not required
Posion value Available via absolute value encoder. Not required
Number of parts in buer storage Should be persistent so the value is not lost in
the event of a reset or program change.
Persistent
Posion of a conveyor line Posion should remain stored. Homing takes
place.
Retain
Example code
VAR RETAIN
remvar1: INT; (* 1. Remanent variable*)
END_VAR
Persistent variables
Persistent variables also remain stored in the event of a stop, restart, online change, or PLC
program download.
Persistent variables are saved when the device is switched o. Persistent variables are
reinialized by execung "RESET origin".
How to create persistent variables:
Precondion
•
Access to »PLC Designer«
1. Right-click on Applicaon.
2. Select New object.
3. Click on Persistent variables.
Example code
VAR_GLOBAL PERSISTENT RETAIN
uiPerRetain : ARRAY[0..1000] OF UINT; (* Declaration of persistent variable*)
END_VAR
Device funcons
Switch-o behavior
Retain variables and persistent variables
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