--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/hysteresis_st.txt	Wed Jun 10 15:02:14 2009 +0200
@@ -0,0 +1,10 @@
+FUNCTION_BLOCK HYSTERESIS
+    (* Boolean hysteresis on difference *)
+    (* of REAL inputs, XIN1 - XIN2      *)
+  VAR_INPUT XIN1, XIN2, EPS : REAL; END_VAR
+  VAR_OUTPUT Q : BOOL := 0; END_VAR
+  IF Q THEN IF XIN1 < (XIN2 - EPS) THEN Q := 0; END_IF ;
+  ELSIF XIN1 > (XIN2 + EPS) THEN Q := 1 ;
+  END_IF ;
+END_FUNCTION_BLOCK
+