Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 84

Connection line
A connection line is a line that connects the end points of FBD element, LD element, and common element.
When connected, the value is passed from the left end to the right end of the line. The data types of the program elements
connected must be identical, or support automatic data type conversion.
Connection point
A connection point is an end point of FBD element, LD element, and common element for connecting them to create an FBD/
LD program.
The left-side end point is for input, and the right-side end point is for output.
Item
Contact
Coil
Variable
Constant
Function
Function block
When connected, the connection point is hidden.
■ I/O point inversion
The input value to a program element or the output value from a program element can be inverted at the connection point.
The connection point where the value is inverted (FALSE to TRUE or TRUE to FALSE) is displayed with a black circle.
The value of the following data types can be inverted: BOOL, WORD, DWORD, ANY_BIT, and ANY_BOOL.
7 FBD/LD
82
7.1 Configuration
Connection point for input

Connection point for output
The return value of the function is not displayed.