--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/sema.txt	Sat Mar 26 18:53:51 2011 +0100
@@ -0,0 +1,25 @@
+(*
+ * (c) 2011 Edouard Tisserant
+ *
+ * Fake semaphore support, for non preemptive implementation.
+ *
+ *)
+
+
+FUNCTION_BLOCK SEMA
+  VAR_INPUT
+    CLAIM : BOOL;
+    RELEASE : BOOL;
+  END_VAR
+  VAR_OUTPUT
+    BUSY : BOOL;
+  END_VAR
+  VAR
+    Q_INTERNAL : BOOL;
+  END_VAR
+
+  Q_INTERNAL := CLAIM OR ( Q_INTERNAL AND (NOT RELEASE));
+  BUSY := Q_INTERNAL;
+
+END_FUNCTION_BLOCK
+