PLC Programming

The Graphic Editors...
Sequence after the ordering according to data flow
When this command is selected the first thing to happen is that the elements are ordered
topographically. A new sequential processing list is then created. Based on the known values of the
inputs, the computer calculates which of the as yet not numbered elements can be processed next. In
the above "network" the block AND, for example, could be processed immediately since the values at
its inputs (1 and 2) are known. Block SUB can only then be processed since the result from ADD must
be known first, etc.
Feedback paths are inserted last.
The advantage of the data flow sequencing is that an output box which is connected to the output of a
block comes immediately after it in the data flow sequencing system which by topological ordering
would not always be the case. The topological ordering can deliver another result in some cases than
ordering by data flow, a point which one can recognise from the above example.
'Extras' 'Create macro''
Symbol:
With this command, several POUs that are selected at the same time can be assembled into a block,
which can be named as a macro. Macros only can be reproduced by Copy/Paste, whereby each copy
becomes a separate macro whose name can be chosen independently. Macros are thus not
references. All connections that are cut by the creation of a macro generate in- or out-pins on the
macro. Connections to inputs generate an in-pin. The default name appears next to the pin in the form
In. For connections to outputs, Out appears. Affected connections which had connection
markers prior to the creation of the macro, retain the connection marker on the PIN of the macro.
At first, a macro has the default name "MACRO". This can be changed in the Name field of the macro
use. If the macro is edited, the name of the macro will be displayed in the title bar of the editor window
appended to the POU name.
5-44 CoDeSys V2.3