Hardy Easy 8 - Manual (Page 13)

Add a Direct Contact from the toolbox by dragging and dropping onto
the rung before (to the left of the function block).
In the Variable Selector box, make the Direct Contact command a
Global variable, name it Do_zero and define it as a Boolean type
variable.
19. To run the Do_Zero command to only once, the Do_zero bit will need to be turned off after
the function block is run. This is accomplished by using a Reset Coil command from the
toolbox. Drag and drop it at the end of the Zero rung and name if Do_Zero when the
variable selector box pops up.