TABLE OF CONTENTS This Appendix outlines the common elements used in IEC 61499 that are based on definitions from the IEC 61131-3 PLC Software Standard. This appendix is provided as a brief overview the formal definitions for all of these elements are given in Part 3 of the IEC 61131 standard.
All textual information should use a restricted set of letters, digits and characters. The standard requires that only characters from standard ISO 646 "Basic code table" are used.
Optionally lower case letters can be used but they are not significant in language elements, for example, Ramp1 and RAMP1 are treated as identical. However lower case letters are still significant if used to define printable strings such as Load Job 1a . Upper and lower case letters can be used within comments.
| Note | In IEC 61499 and IEC 61131-3, identifiers are case insensitive but language keywords are case sensitive and should always be in uppercase. |
Identifiers are used for naming different elements within the IEC languages, for example for naming variables, new data types, function blocks, applications. An identifier can be any string of letters, digits and underlines, provided that:
the first character is not a digit
there are not two or more underline characters together.
The standard provides options for supporting identifiers with lower case letters, and identifiers with a leading underline character. There can be no embedded spaces.
The following are acceptable identifiers:
FBMAIN_P1 INPUT_3PV aEvent1 _APP1
The following are illegal:
FB_PV EX 3PV 1EXpa
The standard states that the...
