1 FUNCTION_BLOCK HYSTERESIS

     2     (* Boolean hysteresis on difference *)

     3     (* of REAL inputs, XIN1 - XIN2      *)

     4   VAR_INPUT XIN1, XIN2, EPS : REAL; END_VAR

     5   VAR_OUTPUT Q : BOOL := 0; END_VAR

     6   IF Q THEN IF XIN1 < (XIN2 - EPS) THEN Q := 0; END_IF ;

     7   ELSIF XIN1 > (XIN2 + EPS) THEN Q := 1 ;

     8   END_IF ;

     9 END_FUNCTION_BLOCK

    10