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The proposal is to presume that the first safety trip is not 'real', but to treat a 2nd one within a given snapshot as real and perform the appropriate safing action. Also, for the first trip, ALERTEN ("Enables cathode control") will be set to zero (i.e. off) and one for the 2nd trip.


detsafety.reset: This is called from icu.ada, will be modified with a second parameter which specifies the value of ALERTEN to be used. It will still be called from icu.ada but now with ALERTEN set to zero. The value of ALERTEN used will be stored in a fixed location visible to the rts system so it can make logic flow decisions and/or use the value itself.

detsafety.alarm: This is called by the limit checking algorithm to determine if there has been a limit violation. On the first trip, it will not return TRUE (thus preventing the limit checking running any recovery rts), but will instead issue an event message saying there has been an alarm, call detsafety.reset (note- as a 'privileged' routine as discussed, and I'll have to sort out the recursion here) with ALERTEN set to one and return FALSE. On the second trip, it will return TRUE and thus allow the error recovery rts to proceed. Note that for the first trip the ALERTFLAG, OPRST and SYSEN flags must be set for it to be considered a trip. For the second, the ALERTFLAG, OPRST, ALERTEN and SYSEN flags must be set for it to be considered a trip.


do_slew will be modified to set the stored value of ALERTEN to zero prior to the call to sfty_reset_slew, thus resetting the safety circuit alarm processing.

safe_to_idle will do a failsafe setting of the stored value of ALERTEN to zero.

The rts sfty_reset_slew (called prior to any filter wheel move and in do_slew ) and sfty_reset (called after a f/w move) will be modified to always use the stored value of ALERTEN. This ensures that they do not erase the value of ALERTEN determined by the Ada routine detsafety.alarm and the rts do_slew.

-- HowardHuckle - 27 Apr 2005

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Topic revision: r5 - 2006-04-26 - HowardHuckle
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