PLC Programming

5 - Editors in CoDeSys
Input Variable
Between the key words VAR_INPUT and END_VAR, all variables are declared that serve as input
variables for a POU. That means that at the call position, the value of the variables can be given along
with a call.
Example:
VAR_INPUT
in1:INT (* 1. Inputvariable*)
END_VAR
Output Variable
Between the key words VAR_OUTPUT and END_VAR, all variables are declared that serve as output
variables of a POU. That means that these values are carried back to the POU making the call. There
they can be answered and used further.
Example:
VAR_OUTPUT
out1:INT; (* 1. Outputvariable*)
END_VAR
Input and Output Variables
Between the key words VAR_IN_OUT and END_VAR, all variables are declared that serve as input
and output variables for a POU.
Attention: With this variable, the value of the transferred variable is changed ("transferred as a pointer", Call-by-
Reference). That means that the input value for such variables cannot be a constant. For this reason,
even the VAR_IN_OUT variables of a function block can not be read or written directly from outside
via .
Example:
VAR_IN_OUT
inout1:INT; (* 1. Inputoutputvariable *)
END_VAR
CoDeSys V2.3 5-3