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Startup Guide - May 2000 B-63003EN-2/01
3
The Advantages of Ladder Language Programming
Designing a sequence program begins with creating a ladder diagram and there are two program entry
methods. One is the entry method with the mnemonic language (PMC instructions such as RD, AND
and OR). The other is the relay symbol method in which the sequence program is entered by using
the relay contact symbols and the functional instruction symbols of the ladder diagram. This can be
done using GE Fanuc’s
FAPT ladder
ladder language software package.
Ladder programming Mnemonic programming
RD X0.0
AND R10.1
OR X6.1
AND.NOT R20.3
WRT Y0.0
vs.
Figure 3 - 4. Comparison of the two modes of program entry
So, if there are two methods of programming, why program using the relay symbols? Here are
several advantages ladder programming offers over mnemonic language programming:
1
.
A program can be understood and developed easily. By
visualizing the program as physical contacts on a ladder
relay, you can see the overall structure of as you progress.
You thereby reduce the effects of two characteristics
inherent to software: invisibility and intangibility.
2
.
A program error can be found easily. The cost of an error increases exponentially in the
software development cycle. The earlier you find your bugs, the less it’s going to cost you.
3
.
It serves as a powerful maintenance tool. When an operation error occurs, you can look at
the relay contacts in the ladder diagram to troubleshoot the problem.