Automatic control function programming manual ladder language

5.2 Network Sequence
5.2.1 General
A ladder network includes:
- an optional label and an optional comment,
- an optional grafcet step,
- a test zone,
- an action zone.
5.2.2 Structure of the Test Zone
5.2.2.1 General
Programming in Ladder Language
The test zone occupies the left-hand side of the network.
It is used to enter logical equations.
A logical equation is a combination of contacts in parallel or in series.
A contact is a Boolean resulting from:
- the test of one or more bit variables,
- the test of the rising or falling edge of an input rung,
- the comparison between two numerical expressions.
The test zone includes six rungs on which six contacts can be connected.
The state of the rung on the contact output depends on the state of the rung on the contact input and the result of the test.
If the result is FALSE, the corresponding rung is set to ZERO. Otherwise the rung state is not changed.
Conditional actions are allowed in the test zone. These actions are determined by the state of the input rung and do
not modify the output rung.
It is possible to branch rungs.
A branch is symbolised by a vertical bar.
5.2.2.2 Contacts
There are five types of contacts:
Contact type Description
{,}7 Test for a ONE state of a list of bit variables.
—] [— IF all the bits are ONE, input rung = output rung.
ELSE, the output rung is reset.
{}7 Test for ZERO state of a list of bit variables.
—] / [— IF all the bits are ZERO, output rung = input rung.
ELSE, the output rung is reset.
Detects the rising edge of the input rung (RISING TRIG).
— R_T — Used to store the state of the input rung.
IF the input rung is a ONE and is a ZERO, the output
rung is set to ONE.
ELSE, the output rung is set to ZERO.
= input rung (storage of the input rung).
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