Motion synchronous actions
10.1 Basics
Job planning
Programming Manual, 07/2010, 6FC5398-2BP40-0BA0
553
10.1.2 Cyclically checking the condition (WHEN, WHENEVER, FROM, EVERY)
Function
A keyword is used to define cyclic checking of the condition of a synchronized action. If no
keyword is programmed, the actions of the synchronized action is performed once in every
IPO cycle.
Keywords
No keyword Execution of the action is not subject to any condition. The
action is executed cyclically in any interpolation cycles.
WHEN
The condition is scanned in each interpolation cycle until it is
fulfilled once, whereupon the associated action is executed
once.
WHENEVER
The condition is checked in cycles in each interpolation cycle.
The associated action is executed in each interpolation cycle
while the condition is fulfilled.
FROM
The condition is checked in each interpolation cycle until it is
fulfilled once. The action is then executed while the synchronous
action is active, i.e. even if the condition is no longer fulfilled.
EVERY
The condition is scanned in each interpolation cycle. The action
is executed once when the condition is fulfilled.
Edge triggering:
the action is executed again when the condition changes from
the FALSE state to the TRUE state.
Main run variables
The variables used are evaluated in the interpolation cycle. Main run variables in
synchronized actions do not trigger a preprocessing stop.
Analysis:
If main run variables occur in a part program (e.g. actual value, position of a digital input or
output etc.), preprocessing is stopped until the previous block has been executed and the
values of the main run variables obtained.
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