Rockwell Automation 1756-IF4FXOF2F ControlLogix High-speed Analog I/O Module - Manual (Page 39)

Rockwell Automation Publication 1756-UM005B-EN-P - January 2013 39
Module Features Chapter 3
Enable Archiving via the Communication Format
To use archiving, you must select the 1756-IF4FXOF2F/B configuration profile,
and then choose the Archiving Connection communication format, as shown in
Figure 6 .
Figure 6 - Archiving Connection Communication Format
The Archiving Connection communication format creates two additional tags in
the input structure of the module, as described below.
Determine RPI
When archiving is enabled, we recommend that you set the requested packet
interval (RPI) of the module at a rate equal to or greater than 20 times the Real
Time Sample (RTS) rate. You can determine the recommended RPI by using the
following equation.
RPI = (RTS x 20)
The fastest RTS rate available for use with the high-speed analog module is
300 μs. If the RTS is set at 300 μs, set the RPI to at least 6 ms or higher as shown
below.
6 ms = (300 μs x 20)
For more information about determining RPI and RTS rates with archiving
enabled, search the Rockwell Automation Knowledgebase for answer ID 40228.
Table 5 - Archiving Tags
Tag Description
I.LastUpdateIndex Returns the number of the last archive sample performed by the module before
data was sent to the controller.
This tag equals 19 when the RPI is greater than (20 * RTS).
I.Input An array that stores channel data for each of the 20 archive samples (0…19).