Assignment :=

Operator - Variable assignment.

Inputs

Input	Data Type	Range	Unit	Default	Description
IN	ANY				Any variable or complex expression.

Outputs

Output	Data Type	Range	Unit	Description
Q	ANY			Forced variable.

Remarks

• The output variable and the input expression must have the same type.
• The forced variable cannot have the read-only attribute.
• In the FBD "Function Block Diagram" A function block diagram describes a function between input variables and output variables. A function is described as a set of elementary blocks and FFLD "Free Form Ladder Diagram" languages, the 1 block is available to perform a 1 gain data copy (1 copy).
• In the IL "Instruction List" This is a low-level language and resembles assembly Language:
  • The FFLD instruction loads the first operand.
  • The ST "Structured text" A high-level language that is block structured and syntactically resembles Pascal instruction stores the current result into a variable.
    • The current result and the operand of ST must have the same type.
• Both FFLD and ST instructions can be modified by N in case of a Boolean operand for performing a Boolean negation.

FBD Language Example

FFLD Language Example

• In the FFLD Language, the input rung (EN) enables the assignment.
  • The output rung keeps the state of the input rung.
• The copy is executed only if EN is TRUE.
• ENO has the same value as EN.

IL Language Example

Op1: FFLD  IN   (* current result is: IN *)
        ST  Q    (* Q is: IN *)
        FFLDN IN1  (* current result is: NOT (IN1) *)
        ST  Q    (* Q is: NOT (IN1) *)
        FFLD  IN2  (* current result is: IN2 *)
        STN Q    (* Q is: NOT (IN2) *)

ST Language Example

Q := IN; (* copy IN into variable Q *)
          Q := (IN1 + (IN2 / IN 3)) * IN4; (* assign the result of a complex expression *)
          result := SIN (angle); (* assign a variable with the result of a function *)
          time := MyTon.ET; (* assign a variable with an output parameter of a function block *)

See Also

Parenthesis (  )