Lenze PC-based Automation Industrial PC - Manual (Page 75)

2.5 EN - 01/2012
L
75
Industrial PC | Parameter setting & configuration
Data integrity in the case of a voltage failure
Retain variables of the PLC
10 Data integrity in the case of a voltage failure
If a voltage failure occurs, important volatile data must not be lost. Therefore the possibil-
ity of saving these data on the CF card is provided. You can also save the data via a PLC func-
tion. Persisting the PLC's retain variables
( 77)
Here you will learn
 what Retain variables of the PLC are,
 how the Backup for systems with UPS functions and
 how the Backup for systems without UPS functions
10.1 Retain variables of the PLC
Retain variables are variables of the PLC which in the case of a voltage failure are saved on
the CF card of the Industrial PC. You can create retain variables in the »PLC Designer« by
marking the variables with the keyword RETAIN.
Variables that are important for the resumption of the production process, and the actual
value of which cannot be read out of the machine because no sensors are available, should
be persistent.
Furthermore this is only reasonable if the value does not change without the influence of
the PLC.
Examples:
Temperature: alters, requires sensors
Position: preferably via absolute encoders
Number of parts within buffer inventory: reasonable for RETAIN.
VAR RETAIN
remvar1:INT; (* 1st remanent variable*)
END_VAR

Note!
For the storage of variables type RETAIN and PERSISTANT a memory area of 1 MB
is available.