7 FBD/LD language
7.1 Configuration
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■The input/output point of a function
• It is necessary that all the input points of a function should be connected to other FBD units over connecting wires.
• The data types of the input variables and output variables of a function should be of certain types. It is necessary that the
FBD units to be connected to the input point or output point should be of the same data types.
• Connect a variable element between an output variable (except for ENO) of a CPU module instruction or module dedicated
instruction and an input variable of another function (or function block).
• In a program that connects a function with EN to another function over a connecting wire, the other function must be a
function with EN and the program must connect ENO and EN over a connecting wire, in order to prevent the function from
using an indefinite value.
LD unit
Units of ladder diagram that can be used in a program of the FBD/LD language are shown below.
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.
AND_E
EN
IN1
IN2
ENO
AND_E
EN
IN1
IN2
ENO
BOOL_OUT_DATA1
BOOL_EN_DATA
bLabel1
bLabel2
bLabel3
(1)
(1) Connect ENO and EN over a connecting wire.
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