FUNCTION_BLOCK "ctd_example"
{ S7_Optimized_Access := 'TRUE' }
VERSION : 0.1
   VAR 
      secTimer {InstructionName := 'TON_TIME'; LibVersion := '1.0'; S7_SetPoint := 'False'} : TON_TIME;
      secTimerQ { S7_SetPoint := 'True'} : Bool;
      secTact : Bool;
      secTimerET : Time;
      testCounter {InstructionName := 'CTD_USINT'; LibVersion := '1.0'; S7_SetPoint := 'False'} : CTD_USINT;
   END_VAR
   VAR RETAIN
      testCounterInt { S7_SetPoint := 'True'} : Int;
   END_VAR
   VAR 
      testCounterQ : Bool;
      chart : Char;
      init : Bool;
   END_VAR

   VAR_TEMP 
      tempInt : Int;
   END_VAR


BEGIN
         // https://www.lamaPLC.com
         // author: Sandor Vamos
         // 12.05.2023, with TIA 16 tested
         // Category: freeware
	// 
	// timer set "secTimerQ" in every second
	#secTimer(IN:=NOT(#secTimerQ),
	          PT:=t#1s,
	          ET=>#secTimerET);
	
	#secTimerQ := #secTimer.Q;
	
	// secTact change state every second
	IF #secTimerQ THEN
	    #secTact := NOT (#secTact);
	END_IF;
	
	// testCounter count down every 2 second (its works with positive edge
	// Q will "true" at 0
	// CV cannot be less than 0 because it is an unsigned SINT counter (CTD_USINT)
	#testCounter(CD:=#secTact,
	             LD:=NOT(#init),
	             PV:=100,
	             Q=>#testCounterQ,
	             CV=>#testCounterInt);
	
	#init := TRUE;
	
	// actual state from testCounter
	#tempInt := #testCounterInt;
	
	
END_FUNCTION_BLOCK