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ProSoft Technology PTQ-AFC User Manual

Page 99

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PTQ-AFC ♦ Modicon Quantum Platform

Quick Start

Liquid and Gas Flow Computer for Hydrocarbon Products

User Manual

ProSoft Technology, Inc.

Page 99 of 259

June 23, 2011

6.11.4 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

… …

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.

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