TABLE OF CONTENTS This appendix summarises the main amendments to the 1993 revision of the IEC 1131-3 standard currently proposed by the IEC Task Force, IEC 65B/WG7/TF3, to go into the second edition of IEC 1131-3 planned to be published in 1999.
At the time of writing this appendix, autumn 1998, these amendments have been incorporated in the second edition of IEC 1131-3. The draft of the second edition will be distributed to national standardisation bodies for review and comment during the spring of 1999. The second edition is planned for publication late summer 1999.
The fact that the IEC is working on new editions of IEC 1131-3 indicates that it is an emerging standard that will continue to be refined and extended as users start to apply the IEC 1131-3 concepts and languages to the development of mainstream control system software.
There are situations where the type of data represented by literal values, such as 12.43, 73, 2#1001, is ambiguous. This is a particular problem in the Instruction List (IL) language; for example, when a literal value is used with a load (LD) instruction, the type of data loaded into the IL register cannot be specified.
It is proposed that all literals can be prefixed with their data type in the form # . Examples are:
SINT#46 (* Short integer literal *) LREAL#12.65 (* Long REAL literal *) PRESSURE#43.2 (* Literal of user type...
