FFLD Coils

Coils are basic graphic elements of the FFLD language.

  • A coil is associated with a Boolean variable displayed above the graphic symbol.
  • A coil performs a change of the associated variable according to the flow on its left-hand side.
  • The possible coil symbols are:

Variable

Coils

Description

Negated

boolVariable

   -(/)-

The associated variable is forced to the negation of the flow on the left of the coil.

Negative Transition

boolVariable

   -(N)-

The associated variable is forced to TRUE if the flow on the left changes from TRUE to FALSE (and forced to FALSE in all other cases).

Normal

boolVariable

   -( )-

The associated variable is forced to the value of the flow on the left of the coil.

Positive Transition

boolVariable

   -(P)-

The associated variable is forced to TRUE if the flow on the left changes from FALSE to TRUE (and forced to FALSE in all other cases).

Reset

boolVariable

   -(R)-

The associated variable is forced to FALSE if the flow on the left is TRUE.

No action if the rung state is FALSE.

  • If the Power Flow on left is TRUE:
  • The horizontal lines are red.
  • The variable above (R) is black.
  • The R and the circle around the R are black.
  • If the Power Flow on left is FALSE and variable above reset coil is NOT Energized (OFF).
  • The horizontal lines are black.
  • The variable above (R) is black.
  • The R and the circle around the R are black.
  • If the Power Flow on left is FALSE and variable above reset coil is Energized (ON).
  • The horizontal lines are black.
  • The variable above (R) is red.
  • The R and the circle around the R are red.

Set

boolVariable

   -(S)-

The associated variable is forced to TRUE if the flow on the left is TRUE.

No action if the flow is FALSE.

  • If the Power Flow on left is TRUE:
  • The horizontal wires on either side of the (S) are red.
  • The variable and the (S) are red.
  • If the Power Flow on left is FALSE and the (S) variable is Energized (ON).
  • The horizontal lines on either sided of (S) are black.
  • The variable and the (S) are red.
  • In all other cases:
  • The horizontal wires are black.
  • The variable and the (S) are black.

  • When a contact or coil is selected, press the Spacebar to change its type (e.g., normal, negated, etc.)

    When the application is running, select a contact and press the Spacebar to swap its value between TRUE and FALSE.



  • Although coils are commonly put at the end, the rung can be continued after a coil.
    The flow is never changed by a coil symbol.