ProSoft Technology PTQ-AFC - Manual (Page 117)

PTQ-AFC ♦ Modicon Quantum Platform Quick Start
Liquid and Gas Flow Computer for Hydrocarbon Products User Manual
ProSoft Technology, Inc. Page 117 of 259
June 23, 2011
6.12.4 Event-triggered archives and accumulator resets
Each archive file (two for each meter) contains an Archive Options bitmap whose
configuration specifies the actions to be scheduled (write archive and/or reset
resettable accumulator(s)) when an event occurs (daily or hourly period-end, or
most loggable events). Archives and/or resets are scheduled only for enabled
meters (with one important clarification; see "Rkv" notes (page 125)). The actions
to be taken upon period-end and those to be taken upon loggable events are
configured separately.
Several archive/reset-triggering events can occur simultaneously. In such cases
the archive or reset occurs only once (an archive is written only when archivable
data has been accumulated for at least one meter scan; additional resets of
already-reset accumulators have no effect).
Scheduled accumulator resets are performed at the top of the meter scan. This
permits their final values to be inspected/fetched/archived while the AFC rotates
its scan among the other meters.
Scheduled archives are written at the top of the meter scan, at its bottom, or
between successive scans, depending on the nature of the triggering event.
Archives written at the top of the scan are written before any accumulator resets.
6.12.5 Period-end events
A "period-end" event is detected by the wallclock. There are two such:
a) "End-of-hour" occurs when the minute of the hour steps into the "End-of-
hour minute" of Site Configuration.
b) "End-of-day" occurs when the minute of the day steps into the "End-of-day
minute" of Site Configuration.
A wallclock change that skips forward over an end-of-period minute will cause
that period-end to be missed, and a change that skips backward over that minute
will cause that period-end to be repeated, so wallclock adjustments should be
performed at times well-removed from either end-of-period minute.
Though a period-end event is not recorded in the event log, it does cause
archives and resets to be scheduled for all enabled meters according to their
configured "period-end" Archive Options. Archives and resets scheduled by
period-end are delayed in their action until at least one meter scan has occurred
after the event (the archive data accumulation that takes place at the end of the
meter scan also records the latest timestamp, so the written archive then reflects
the fact that the period-end has occurred).