ProSoft Technology MVI56-AFC - Manual (Page 95)

MVI56-AFC ♦ ControlLogix Platform Archives
Liquid and Gas Flow Computer User Manual
ProSoft Technology, Inc. Page 95 of 316
February 25, 2011
8.4 Archive Order
An important concept regarding this topic is the archive order. Understanding this
simple concept is essential when reading archive data (through the backplane or
Modbus Master). Each archive has a number (its "age") that labels its position in
the archive queue. The following table shows the archive numbering scheme
(both daily and hourly archives):
Archive Age Register Types Description
0 Holding Register Current archive.
1 Input Register Most recent archive
2 Input Register Second most recent archive
3 Input Register Third most recent archive
4 Input Register Fourth most recent archive
(and so forth)
The archive 0 is the current archive. Because its period has not been concluded
its closing timestamp and values (such as accumulator, average temperature,
etc…) will be continuously updated. After the period is over (or an event occurs
depending on the archive configuration) the data in archive 0 will be saved as the
"new" archive 1. The data in the "old" archive 1 will be saved as the new archive
2 and so forth.
The current archive is stored in the primary slave's holding register bank. The
past archives are stored in the primary slave's input register bank.
The following illustration shows an example for hourly archives:
Where:
OT = Opening Time Stamp
CT = Closing Time Stamp
The previous figure shows an example where the hourly archives are configured
to be generated upon period-end at the minute "0" (1:00, 2:00, 3:00, etc…).
Therefore, at 09:59:59 the archive 0 (current archive) is just about to be saved as
the "new" archive 1.