Rockwell Automation T80016 Application Note Maintenance Override Programming - Manual (Page 8)

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AN-T80016 Maintenance Override Programming
Issue 1 June 08 AN-T80016 8
Program Code
(*
------------------------------DETAILS--------------------------------
NAME :DI_COND
REVISION :1
CREATED BY :Nick Owens
DATE :18/03/08
LAST EDITED BY :
DATE :
REVIEWED BY :
DATE :
TYPE :Function Block
LANGUAGE :Structured Text
------------------------------DESCRIPTION----------------------------
Digital input processing function block with Maintenance Override for AN-T80016.
This function block includes the following functions:
Detection of input trip, resettable when clear or overridden.
Maintenance override: non-timed, with an acknowledge/confirm handshake to set,
separate override enable, and limit to the maximum current overrides in a safety
group.
Detailed descriptions of each function are given in the code comments
below.
------------------------------VARIABLES------------------------------
Note: GLOBAL variables must be added to the project global dictionary
as they are not owned by the block!
GLOBAL :
None.
(MC, MOE and RST could be made globals to save on input connections, since all
instances
will use the same variables.)
LOCAL : defined in function block's local dictionary
(Signals are active in the TRUE state unless stated otherwise)
Last_ORQ
Boolean, Internal Override Request at previous scan for edge
detection
Last_MC
Boolean, Internal Override Confirm at previous scan for edge
detection
OR_Timer
Timer, Internal Time limit on DCS Override Request
Int_OS Boolean, Internal Internal copy of Override Status
Int_OA Boolean, Internal Internal copy of Override Acknowledge
Int_OS is used as an internal copy of OS (Override Status) since function block
outputs can't be read from. Int_OA is an internal copy of OA for the same reason.