Maintenance Override Programming Manual

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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

void 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