Trusted – Rockwell Automation T80016 Application Note Maintenance Override Programming User Manual

Page 10

Trusted

AN-T80016 Maintenance Override Programming

Issue 1 June 08

AN-T80016

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 *)

(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 *)

NOT

GOA

(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 *)

NOT

MOE

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