Automatic control function programming manual ladder language

5.1 Elements Common to All Types of Sequence
5.1.1 Sequence Header
Programming in Ladder Language
Sequences such as tables of constants, character strings and networks have a common header including:
- an optional sequence identifier called a label (see Sec. 4.2),
- an optional comment (see Sec. 4.2),
- an optional grafcet step (see Sec. 4.3).
5.1.2 Grafcet Step
Grafcet steps increase the speed of execution of a programme because inactive sequences are not executed. Grafcet
steps are used to specify the software using a grafcet methodology.
If it not possible to programme all the actions of a grafcet step in the same sequence, the programmer can write as
many sequences as he desires with the same step number.
5.1.2.1 General
A sequence with a grafcet step has two possible states:
- active when == ,
- inactive when != .
5.1.2.2 How the System Processes Grafcet Steps
When a sequence with a grafcet step is active, the system executes it like a sequence without a step.
When a sequence with a grafcet step is inactive, it is not executed.
Label comment
%M2.W == 5 ?
(System test)
YES
NO
%M2.W 5
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5