<4. Control Application Creation>
These five languages can be broadly classified into continuous execution languages
and step execution languages. FBD, LD, IL and ST belong to the former group,
whereby application content is executed continuously, while ST belong to the latter
group, whereby application content is segmented into and executed as steps.
FBD, LD, IL and ST can be further classified into graphical languages and text-
based languages, with FBD, LD belonging to the former group, and ST, IL belonging
to the latter group.
(Function Block Diagram)
LD (Ladder Diagram)
ST (Structured Text)
IL (Instruction List)
(Sequential Function Chart)
Continuous
execution
languages
TIP
As IL is seldom used in practice, descriptions about continuous execution language type hereinafter will
be limited to three programming languages, namely, FBD, LD and ST.
4.2.2 Selecting a Programming Language
Logic Designer allows programming language to be selected on logical POU
(program, function, function block) basis. When using SFC, programming language
can also be selected on transition or action basis. While a programmer may select
any language according to preference, it is important to select a language suited for
a specific purpose to fully exploit its unique features. For details on selection of
programming language, see Section 8.4, “Criteria for Selecting Programming
Languages in Logic Designer.”
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