Program Elements - Mitsubishi Electric MELSEC iQ-R Series Programming Manual

Program elements

FBD elements
The following table lists FBD elements consisting an FBD/LD program.
Item
Variable
Constant
Function (FUN)
Function block (FB)
■ Data type of constant elements
The data type of the value input to a constant is not determined when the value is input. It is determined when the constant
element is connected to another FBD element with a connection line. The data type will be the same as that of the connected
FBD element.
Ex.
When the constant value is 1
The possible data types are BOOL, WORD, DWORD, INT, DINT, REAL, and LREAL, but the data type of the input value
cannot be determined at this point. The data type is determined when the constant is connected to another FBD element.
(1)
(2)
■ Automatic conversion of data type
If the data types differ between connected elements, one data type may be converted automatically.
To prevent data from being lost during type conversion, conversion is performed only from a smaller size data type to a larger
size data type. The data type automatic conversion processing in FBD/LD is same as that in ST language. For details, refer to
the following.
Page 63 Automatic conversion of data type
7 FBD/LD
76
7.1 Configuration
Description
Stores a value. A specific data type is assigned to each variable, and only data of the assigned
data type are stored.
Labels and devices can be specified as a variable.
Outputs a specified value.
Executes a function.
• How to create functions ( GX Works3 Operating Manual)
• Standard functions ( MELSEC iQ-R Programming Manual (Instructions, Standard Functions/
Function Blocks))
Executes a function block.
• How to create function blocks ( GX Works3 Operating Manual)
• Standard function blocks ( MELSEC iQ-R Programming Manual (Instructions, Standard
Functions/Function Blocks))
• Module function blocks ( Function Block Reference for the module used)
(1) The data type has not been determined.
(2) INT data type
(3) INT data type
(3)