Can function blocks also have execution control variables EN and ENO, like functions?
The standard is not explicit about whether function blocks may have execution control variables, e.g. for connecting function blocks within ladder rungs. However, from the IEC 1131 languages user guidelines, (part 8 of the IEC 61131 standard), it is implied that for consistency, both functions and function blocks should use EN and ENO variables for execution control in ladder diagrams. It is an implementation decision whether function blocks have EN and ENO variables that can be used in the FBD language for explicit execution control. This may be useful in eliminating execution order ambiguities that might arise in FBD networks. • In a full graphic implementation of FBD, is there anyway to distinguish between lines that cross-over and lines that join. The graphical format of lines, cross-overs and junctions in full graphics implementations of languages LD, FDB and SFC is not specified in IEC 61131-3. It is a implementation decision outside the scope of the standard how fine graphic det
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- Can function blocks also have execution control variables EN and ENO, like functions?
