Rockwell Automation 1756-IF4FXOF2F ControlLogix High-speed Analog I/O Module - Manual (Page 38)

38 Rockwell Automation Publication 1756-UM005B-EN-P - January 2013
Chapter 3 Module Features
Archiving
Archiving is an input scanning function that lets the high-speed analog module
store as many as 20 input data samples for each channel in the module’s on-board
buffers before it sends the I/O data to the controller.
By storing the channel data until 20 samples are taken, the module lengthens the
time between I/O data transfers, resulting in a better use of controller task
resources by batching the samples into 1 large transfer rather than 20 small
transfers.
When a Real Time Sample (RTS) period is defined during configuration, it
defines the interval in which the module scans for new data from each of the
input channels, for example, RTS period = one input data sample per channel.
Without archiving, the module sends this channel data at the completion of
every channel scan, for example, every RTS period. Because archiving permits the
module to store 20 channel scans worth of data on-board before transferring it to
the controller, the system can effectively record channel data without excessively
burdening the backplane or controller.
IMPORTANT Archiving is available only with the following:
• Module firmware revision 3.005 or later
For more information about upgrading a series A module with series B
firmware, see
Appendix F .
• RSLogix 5000 software version 16.03.00 or later, or the Studio 5000
environment version 21.00.00 or later
EXAMPLE If the module is set to scan its channels at the fastest rate possible, for
example, RTS = 300 μs, rather than sending data to the controller at that
frequency, the module sends data as defined by this formula:
Archive data transfer rate = 20 x RTS chosen by the user
In this case, with the RTS period for high-speed analog module = 300 μs, the
module fills its on-board buffers with data at the rate defined by that RTS, but
transfers the data to the controller only every 6 ms (20 samples x 300 μs).
IMPORTANT The high-speed scanning that occurs when archiving applies only to the inputs
on the module and not the outputs. The outputs are updated at the RPI rate.