→Retentive and non-retentive variable: RETAIN, NON_RETAIN
Retentive variables are variables that are stored in a way that their values are conserved without changes for a →warm restart after the application has been stopped. Non-retentive variables are initialized anew with their →initial value, in case of a warm restart.
Declaration of |
in ST-editor, by using a keyword |
in a graphical editor, by using a prefix |
retentive →variables |
RETAIN |
R |
non-retentive variables
|
NON_RETAIN |
NR |
The keywords are only allowed for the sections
VAR
,
VAR_INPUT
,
VAR_OUTPUT
and
VAR_GLOBAL
but also for declared →function block instances. They are
not allowed for program instances within the
PLC-object
.
The prefix is only allowed for internal variables,
→input variables
,
→output variables
and
→global variables
.