PROGRAM GRAVEL  (* Gravel measurement and loading system *)
 VAR_INPUT
    OFF_PB         : BOOL ;
    ON_PB          : BOOL ;
    FILL_PB        : BOOL ;
    SIREN_ACK      : BOOL ;
    LOAD_PB        : BOOL ; (* Load truck from bin *)
    JOG_PB         : BOOL ;
    LAMP_TEST      : BOOL ;
    TRUCK_ON_RAMP  : BOOL ; (* Optical sensor *)
    SILO_EMPTY_LS  : BOOL ;
    BIN_EMPTY_LS   : BOOL ;
    SETPOINT       : BYTE ; (* 2-digit BCD *)
 END_VAR
 VAR_OUTPUT
    CONTROL_LAMP    : BOOL ;
    TRUCK_LAMP      : BOOL ;
    SILO_EMPTY_LAMP : BOOL ;
    CONVEYOR_LAMP   : BOOL ;
    CONVEYOR_MOTOR  : BOOL ;
    SILO_VALVE      : BOOL ;
    BIN_VALVE       : BOOL ;
    SIREN           : BOOL ;
    BIN_LEVEL       : BYTE ;
 END_VAR
 VAR
  BLINK_TIME : TIME; (* BLINK ON/OFF time *)
  PULSE_TIME : TIME; (* LEVEL_CTR increment interval *)
  RUNOUT_TIME: TIME; (* Conveyor running time after loading *)
  RUN_IN_TIME: TIME; (* Conveyor running time before loading *)
  SILENT_TIME: TIME; (* Siren silent time after SIREN_ACK *)
  OK_TO_RUN  : BOOL; (* 1 = Conveyor is allowed to run *)
  (* Function Blocks *)
  BLINK: TON; (* Blinker OFF period timer / ON output *)
  BLANK: TON; (* Blinker ON period timer / blanking pulse *)
  PULSE: TON; (* LEVEL_CTR pulse interval timer *)
  SIREN_FF: RS;
  SILENCE_TMR: TP; (* Siren silent period timer *)
 END_VAR
 VAR RETAIN LEVEL_CTR : CTU ; END_VAR
   (* Program body *)
   (* Major operating states *)
   INITIAL_STEP START : END_STEP
   TRANSITION FROM START TO FILL_BIN
      := FILL_PB & CONTROL.X ; END_TRANSITION
   STEP FILL_BIN: SILO_VALVE(N); END_STEP
   TRANSITION FROM FILL_BIN TO START
      := NOT FILL_PB OR NOT CONTROL.X ; END_TRANSITION
   TRANSITION FROM FILL_BIN TO LOAD_WAIT := LEVEL_CTR.Q ;
   END_TRANSITION
   STEP LOAD_WAIT : END_STEP
   TRANSITION FROM LOAD_WAIT TO RUN_IN
      := LOAD_PB & OK_TO_RUN ; END_TRANSITION
   STEP RUN_IN : END_STEP
   TRANSITION FROM RUN_IN TO LOAD_WAIT := NOT OK_TO_RUN ;
   END_TRANSITION
   TRANSITION FROM RUN_IN TO DUMP_BIN
      := RUN_IN.T > RUN_IN_TIME;
   END_TRANSITION
   STEP DUMP_BIN: BIN_VALVE(N); END_STEP
   TRANSITION FROM DUMP_BIN TO LOAD_WAIT := NOT OK_TO_RUN ;
   END_TRANSITION
   TRANSITION FROM DUMP_BIN TO RUNOUT := BIN_EMPTY_LS ;
   END_TRANSITION
   STEP RUNOUT : END_STEP
   TRANSITION FROM RUNOUT TO LOAD_WAIT := NOT OK_TO_RUN ;
   END_TRANSITION
   TRANSITION FROM RUNOUT TO START
      := RUNOUT.T >= RUNOUT_TIME ; END_TRANSITION
(* Control state sequencing *)
INITIAL_STEP CONTROL_OFF: END_STEP
TRANSITION FROM CONTROL_OFF TO CONTROL
     := ON_PB & NOT OFF_PB ; END_TRANSITION
STEP CONTROL: CONTROL_ACTION(N); END_STEP
ACTION CONTROL_ACTION:
   BLINK(EN:=CONTROL.X & NOT BLANK.Q, PT := BLINK_TIME) ;
   BLANK(EN:=BLINK.Q, PT := BLINK_TIME) ;
   OK_TO_RUN := CONTROL.X & TRUCK_ON_RAMP ;
   CONVEYOR_MOTOR :=
     OK_TO_RUN & OR(JOG_PB, RUN_IN.X, DUMP_BIN.X, RUNOUT.X);   
END_ACTION
TRANSITION FROM CONTROL TO CONTROL_OFF := OFF_PB ;
END_TRANSITION
(* Monitor Logic *)
INITIAL_STEP MONITOR: MONITOR_ACTION(N); END_STEP
ACTION MONITOR_ACTION:
  CONVEYOR_LAMP := CONVEYOR_MOTOR & BLINK.Q ;
  CONTROL_LAMP := CONTROL.X OR LAMP_TEST ;
  TRUCK_LAMP := TRUCK_ON_RAMP OR LAMP_TEST ;
  SILO_EMPTY_LAMP := BLINK.Q & SILO_EMPTY_LS OR LAMP_TEST ;
  SILENCE_TMR(IN:=SIREN_ACK, PT:=SILENT_TIME) ;
  SIREN_FF(S:=SILO_EMPTY_LS, R1:=SILENCE_TMR.Q) ;
  SIREN := SIREN_FF.Q1 ;
  PULSE(IN:=FILL_BIN.X & NOT PULSE.Q, PT:=PULSE_TIME) ;
  LEVEL_CTR(R := BIN_EMPTY_LS, CU := PULSE.Q,
            PV := BCD_TO_INT(SETPOINT)) ;
  BIN_LEVEL := INT_TO_BCD(LEVEL_CTR.CV) ;
END_ACTION

END_PROGRAM

 CONFIGURATION GRAVEL_CONTROL
   RESOURCE PROC1 ON PROC_TYPE_Y
     PROGRAM G : GRAVEL
      (* Inputs *)
       (OFF_PB        := %I0.0 ,
        ON_PB         := %I0.1 ,
        FILL_PB       := %I0.2 ,
        SIREN_ACK     := %I0.3 ,
        LOAD_PB       := %I0.4 ,
        JOG_PB        := %I0.5 ,
        LAMP_TEST     := %I0.7 ,
        TRUCK_ON_RAMP := %I1.4 ,
        SILO_EMPTY_LS := %I1.5 ,
        BIN_EMPTY_LS  := %I1.6 ,
        SETPOINT      := %IB2  ,
       (* Outputs *)
        CONTROL_LAMP    => %Q4.0,
        TRUCK_LAMP      => %Q4.2,
        SILO_EMPTY_LAMP => %Q4.3,
        CONVEYOR_LAMP   => %Q5.3,
        CONVEYOR_MOTOR  => %Q5.4,
        SILO_VALVE      => %Q5.5,
        BIN_VALVE       => %Q5.6,
        SIREN           => %Q5.7,
        BIN_LEVEL       => %B6) ;
   END_RESOURCE
 END_CONFIGURATION