Lenze PLC Designer PLC Designer (R3-1) - Manual (Page 745)

L-force | PLC Designer
General Editors
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DMS 4.1 EN 03/2011 TD29 743
Symbol generation:
In the element properties of a step or an action you can define, whether for the step or
action name flag a symbol definition should be added to a possibly created and
downloaded symbol application. For this purpose make an entry for the desired access
right in column "Symbol" of the element properties view.
Note: The flags described above might be used to force a certain status value for a
step, that is for setting an step active, but be aware that this will effect uncontrolled
states within the SFC !
Time via TIME variables:
The flag "t" gives the current time span which has passed since the step had got active;
this is only for steps, no matter whether there is a minimum time configured in the
step attributes or not (see also below: SFCError)
For steps: <stepname>.t (<stepname>._t not usable for external purposes)
For actions: the implicit time variables are not used.
Control of SFC execution (timeouts, reset, tip mode)
Some implicitly available variables, also named SFC flags, (see table below) can be used
to control the operation of an SFC, for example for indicating time overflows or
enabling tip mode for switching transitions.
In order to be able to access these flags and to get them work, they must be declared
and activated. This is to be done in the SFC Settings dialog which is a subdialog of the
object properties dialog. Manual declaration, as it was needed in V2.3, is only
necessary to enable write access from another POU (see below, Accessing flags). In this
case however regard the following: If you declare the flag globally, you must
deactivate the "Declare" option in the SFC Settings dialog in order not to get a
implicitly declared local flag, which then would be used instead of the global one !
Keep in mind, that the SFC Settings for a SFC POU initially are determined by the
definitions currently set in the SFC opfions dialog.
Notice that a declaration of a flag variable solely done via the SFC Settings dialog will
only be visible in the online view of the SFC POU !
Example of the use of SFCError
There is a SFC POU named "sfc1" containing a step "s2" which has time limits defined
in its step attributes. See the attributes displayed below in figure "Online view of SFC
sfc1".
If for any reason the step s2 stays active for a longer time than allowed by its time
properties (time overflow), a SFC flag will be set which might be read by the
application.