7 FBD/LD LANGUAGE
7.1 Configuration
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7
LD unit
Units of ladder diagram that can be used in a program of the FBD/LD language are shown below.
■The AND operation and OR operation of a contact symbol
A contact symbol executes an AND operation or an OR operation depending on the status of the connection of a circuit chart.
This is reflected in the operation result.
• In the case of a series connection (1), an AND operation is executed with the operation results so far. This will be the
operation result.
• In the case of a parallel connection (2), an OR operation is executed with the operation results so far. This will be the
operation result.
Unit Symbol Description
Left bus This is an unit to represent a bus. This is the starting point to create a ladder circuit.
NO contact Turns on when a specified device or label is ON.
NC contact Turns on when a specified device or label is OFF.
Rising edge Turns on at the rising edge (OFF to ON) of a specified device or label.
Falling edge Turns on at the falling edge (ON to OFF) of a specified device or label.
Negated rising edge Turns on when a specified device or label is OFF or ON, or at the falling edge (ON to OFF) of a
specified device or label.
Negated falling edge Turns on when a specified device or label is OFF or ON, or at the rising edge (OFF to ON) of a
specified device or label.
Coil Outputs an operation result to a specified device or a label.
Complementing coil When the operation result turns OFF, the specified device or label turns ON.
Set When the operation result turns ON, the specified device or label turns ON.
The device or the label that turns ON remains ON even if the operation result turns OFF.
Reset When the operation result turns ON, the specified device or label turns OFF.
When the operation result is OFF, the status of the device or the label does not change.
(1) Series connection contact
(2) Parallel connection contact
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