:=   LD   LDN   ST   STN

Operator - variable assignment.


IN : ANY Any variable or complex expression


Q : ANY  Forced variable


The output variable and the input expression must have the same type. The forced variable cannot have the "read only" attribute.  In LD and FBD languages, the "1" block is available to perform a "1 gain" data copy. In LD language, the input rung (EN) enables the assignment, and the output rung keeps the state of the input rung. In IL language, the LD instruction loads the first operand, and the ST instruction stores the current result into a variable. The current result and the operand of ST must have the same type. Both LD and ST instructions can be modified by "N" in case of a boolean operand for performing a boolean negation.

ST Language

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 *)

FBD Language

1Fbd.gif (1117 octets)

LD Language

(* The copy is executed only if EN is TRUE *)
(* ENO has the same value as EN *)
1Ld.gif (1375 octets)

IL Language:

Op1: LD  IN   (* current result is: IN *)
     ST  Q    (* Q is: IN *)
     LDN IN1  (* current result is: NOT (IN1) *)
     ST  Q    (* Q is: NOT (IN1) *)
     LD  IN2  (* current result is: IN2 *)
     STN Q    (* Q is: NOT (IN2) *)

See also