Rockwell Automation T80016 Application Note Maintenance Override Programming - Manual (Page 10)

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AN-T80016 Maintenance Override Programming
Issue 1 June 08 AN-T80016 10
the time limit has not been reached and a group override is available and
maintenance overrides are enabled, set the override and clear down the request.
This logic checks that the override request went True on a previous scan, to
avoid setting overrides without acknowledgement *)
IF (ORQ AND Last_ORQ) AND Int_OA AND (MC AND NOT Last_MC) AND GOA AND MOE AND
NOT Int_OS AND OR_Timer < t#30s
THEN
Int_OS := True;
TSTOP(OR_Timer);
OR_Timer := t#0s ;
Int_OA := False;
END_IF ;
(* If there is no group override available, abort any override request *)
(* If an overide request is in progress and the timer has run out, clear down the
override request *)
IF NOT GOA OR (Int_OA AND OR_Timer >= t#30s ) THEN
TSTOP(OR_Timer);
OR_Timer := t#0s ;
Int_OA := False ;
END_IF ;
(* If the Maintenance Override Enable keyswitch is set to Disable, or the
override request has been removed, remove the ovveride and abort any override
request *)
IF NOT MOE OR NOT ORQ THEN
Int_OS := False ;
TSTOP(OR_Timer);
OR_Timer := t#0s ;
Int_OA := False ;
END_IF ;
(* Report override status and acknowledge to DCS *)
OS := Int_OS;
OA := Int_OA;
(* Record state of Override Request OR and Override Confirm MC for next scan
to detect rising/falling edges *)
Last_ORQ := ORQ;
Last_MC := MC;
(*
Safety Trip