Maintenance Override Programming Manual

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AN-T80016 Maintenance Override Programming
Issue 1 June 08 AN-T80016 7
Logic Chart
This table presents the logic in a similar way to Cause and Effect charts. It is recommended to analyse
the logic requirements of a function block before programming, because the resulting program will be
more reliable and robust to unusual combinations of inputs and internal states. List all inputs, all
p
revious values of inputs
Blank boxes in the table indicate ‘don’t care’ for that input.
OR MC GOAMOE OS OA Timer Implications Action
F
Maintenance Override disable
Clear OS, zero/stop timer,clear
OA
F>T T T
Override requested and
enabled
Set OA, start timer
T>
T F>T
T T F T <30s
Override confirmed Clear OA, set OS, zero/stop timer
F
Override cancelled
Clear OS, clear OA,zero/stop
timer
T F T >30s
Override timer ran out Clear OA, zero/stop timer
T F F T
No group override available Clear OA, zero/stop timer
The trip logic may be treated separately.
DI RS OS
T T
Reset trip when input clear Set DT
T T
Reset trip when Override set Set DT
F F
Input tripped and no override Clear DT