(* Timers: TON vs TOF vs RTO — Control Panel scene
   X1 = Start (N.O.)   X2 = Stop (N.C., TRUE when not pressed)
   X3 = Jog button, used here as Service Reset   Y1 = Motor run
   IEC 61131-3 has TON and TOF but no retentive timer, so the run-time
   total is built from a TON that times each run plus a banked total. *)
VAR
  RunRequest : BOOL;
  StartDelay : TON;     // 2 s on-delay before the motor starts
  RunOn      : TOF;     // 5 s run-on after the run request drops
  RunTimer   : TON;     // times the current run only
  Banked     : TIME;    // run time from every earlier run
  RunTotal   : TIME;    // retentive total = banked + current run
  ServiceDue : BOOL;
END_VAR

(* Run request — Start seals in; Stop or Service Due drops it *)
RunRequest := (X1 OR RunRequest) AND X2 AND NOT ServiceDue;

(* TON — the run request must be ON for 2 s before the motor starts *)
StartDelay(IN := RunRequest, PT := T#2s);

(* TOF — Q turns ON with the start delay and holds for 5 s after it drops *)
RunOn(IN := StartDelay.Q, PT := T#5s);
Y1 := RunOn.Q;

(* Retentive total — while running, add this run to the bank;
   when stopped, the total is kept in Banked *)
RunTimer(IN := Y1 AND NOT X3, PT := T#24h);
IF Y1 THEN
  RunTotal := Banked + RunTimer.ET;
ELSE
  Banked := RunTotal;
END_IF;

(* Service reset — X3 clears the total, like a RES on an RTO *)
IF X3 THEN
  Banked := T#0s;
  RunTotal := T#0s;
END_IF;

ServiceDue := RunTotal >= T#20s;