Lenze PLC Designer PLC Designer (R2-x) - Manual (Page 65)

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DMS 3.2 EN 02/2011 TD29 63
Transition / Transition condition
Between the steps there are so-called transitions.
A transition condition must have the value TRUE or FALSE. Thus it can consist of either
a boolean variable, a boolean address or a boolean constant. It can also contain a
series of instructions having a boolean result, either in ST syntax (e.g. (i<= 100) AND b)
or in any language desired (see 'Extras' 'Zoom Action/Transition'). But a transition may
not contain programs, function blocks or assignments!
In the SFC-Editor a transition condition can be written directly at the transition symbol
or an own editor window can be opened for entering the condition (see chapter 5.4.4,
'Extras' 'Zoom Action/Transition'). Regard that the instructions entered in the editor
window will take precedence!
Note!
Besides transitions, inching mode can also be used to skip to the next step; see
SFCtip and SFCtipmode.
Active step
After calling the SFC POU, the action (surrounded by a double border) belonging to the
initial step is executed first. A step, whose action is being executed, is called active. In
Online mode active steps are shown in blue.
In a control cycle all actions are executed which belong to active steps. Thereafter the
respective following steps of the active steps become active if the transition
conditions of the following steps are TRUE. The currently active steps will be executed
in the next cycle.
Note!
If the active step contains an output action, this will only be executed during the
next cycle, provided that the transition following is TRUE.
Regard the possibility to use implicit variables for scanning the status and time of
steps resp. actions.