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1. System summary
1.4.1 Programming languages
Programming
languages
Statement list (STL)
Structured text (ST)
Sequential function chart
(SFC)
Function diagram (FUN)
or
Free−graphic function
diagram (CFQ)
Ladder diagram (LDR)
Tab. 1/3:
Programming languages of CoDeSys provided by Festo
Festo P.BE−CPX−CEC−EN en 1004a
CoDeSys provided by Festo offers five of the programming
languages standardised in IEC 61131−3, see Tab. 1/3. Each of
these programming languages has certain characteristics
that are especially suited for solving specific tasks.
Type
Description
Text−based
The statement list enables the programmer to de
scribe the working steps of controller functions with
programming
language
simple instructions. The language structure supports
the efficient handling of complex tasks.
Structured text comes closest to the programming
languages used for the PC, such as Pascal and C.
It consists of a number of statements that can be
performed conditionally ("IF..THEN..ELSE") or in loops
(WHILE..DO), as in high−level languages.
Graphic
Enables programming of sequences and so is suited
programming
for structuring and organising projects. With transi
languages
tions and connections, the sequential function chart
describes the time sequence of the various steps
within the program.
The function diagram works with a list of networks,
whereby each network contains a structure that de
picts a logical or arithmetic expression, calls up a
function module, a jump or a return instruction.
In addition, based on the function diagram, there is
the free−graphic function diagram (CFC), in which the
elements are freely placed and feedback can be
directly added.
The ladder diagram was developed from the circuit
diagram. The diagram of a LDR program is therefore
similar to the diagram of a circuit diagram in relation
to the diagram of logical links.
1−11
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