Lenze PLC Designer PLC Designer (R3-1) - Manual (Page 248)

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246 DMS 4.1 EN 03/2011 TD29
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When the command gets executed, the following will happen internally: First the
elements are ordered topographically. Then a new sequential processing list will be
created. Based on the known values of the inputs, the computer calculates which of
the not yet numbered elements can be processed next. In the above shown "network"
e.g. the ADD block (0) could be processed immediately since the values at its inputs ("1"
and "2") are known. Block SUB (1) can only be processed afterwards since the result
from ADD must be known first, etc. Feedback paths get inserted last. So a sequencing
by data flow will result.
Order By Topology
This command (category CFC) per default is part of submenu "Execution Order" in the
CFC menu. It effects that the execution order in the CFC-Editor is determined by the
topological order of the elements and not by the data flow.
Topological order means that the execution order, that is the processing of the
elements runs from left to right and from top to bottom. The element numbers
indicating the position of an element within the processing list, increase from left to
right and from top to bottom. The position of the connection lines is not relevant, only
the location of the elements is important.
When the command is executed, implicitly all currently selected elements get removed
from the processing list and then re-inserted one by one in the remaining list from
bottom right through to upper left. In doing so each selected element will be entered
before its topological successor and the numbers of the remaining elements will be
adapted.
Example, Topological arranging of selected elements
Abb. 81 Sequence before
The elements with numbers 1, 2 and 3 are selected. If now the command 'Order By
Topology' is executed, the elements first will be taken out of the sequential processing
list. The subsequent re-inserting will be done conversely: