Lenze PLC Designer PLC Designer (R2-x) - Manual (Page 66)

L-force | PLC Designer
What is What in PLC Designer
64 DMS 3.2 EN 02/2011 TD29

IEC step
Along with the simplified steps the standard IEC steps in SFC are available.
In order to be able to use IEC steps, you must link the special SFC library lecsfc.lib into
your project.
Not more than nine actions can be assigned to an IEC step. IEC actions are not fixed as
input, step or output actions to a certain step as in the simplified steps, but are stored
separately from the steps and can be reused many times within a POU. For this they
must be associated to the single steps with the command 'Extras''Associate action'.
Along with actions, Boolean variables can be assigned to steps.
The activation and deactivation of actions and boolean variables can be controlled
using so-called qualifiers. Time delays are possible. Since an action can still be active, if
the next step has been processed, for example through the qualifier S (Set), one can
achieve concurrent processes.
An associated boolean variable is set or reset with each call of the SFC block. That
means, that at each call the variable gets re-assigned value TRUE resp. FALSE.
The actions associated with an IEC step are shown at the right of the step in a two-
part box. The left field contains the qualifier, possibly with time constant, and the
right field contains the action name respectively boolean variable name.
An example for an IEC step with two actions:
In order to make it easier to follow the processes, all active actions in online mode are
shown in blue like the active steps. After each cycle a check is made to see which
actions are active.
Pay attention here also to the restrictions on the use of time-qualifiers in actions that
are repeatedly re-used within the same cycle (see 'Qualifier')!
Note!
If an action has been inactivated, it will be executed once more. That means, that
each action is executed at least twice (also an action with qualifier P).
In case of a call first the deactivated actions, then the active actions are executed, in
alphabetical order each time.