Rockwell Automation 1756-OF8I ControlLogix Eight-channel Isolated Analog I/O Modules - Manual (Page 57)

Rockwell Automation Publication 1756-UM540A-EN-P - May 2014 57
1756-IF8I Isolated Analog Input Module Chapter 3
Synchronized Sampling
This feature lets you synchronize input sampling across inputs on multiple
modules in the same chassis, forcing those inputs to sample simultaneously
within approximately 20
μ
S of each other.
For example, if you have 12 input devices connected to one 1756-IF8I module
and two 1756-IRT8I modules in the same chassis, or different chassis
synchronized to the same CIP Sync TimeMaster, use Synchronized Sampling to
take a snapshot of the input data available at each input at a single moment in
time.
The following conditions must exist to use this feature:
• A 1588 CIP Sync Time Master is configured for the chassis.
• All modules in the set use the same RPI value or values that are multiples
of each other.
• Synchronized Sampling with Other Synchronized Modules is enabled for
all input channels in the set.
For these input modules, configuring one channel for Synchronized
Sampling synchronizes all eight channels.
While setting the RPI to the same value on all 1756-IF8I modules guarantees
that each module samples at the same rate, it does not guarantee that they sample
at the same time. When enabled, Synchronized Sampling provides each module a
synchronized starting point for its respective input scans. Because the RPI values
are the same, the inputs on the modules are sampled at the same rate and the same
time.
To see where to enable Synchronized Sampling, see page 127 .
IMPORTANT Synchronized Sampling is not limited to input sample across inputs on the
same module types.
You can use Synchronized Sampling across inputs on 1756-IF8I modules and
1756-IRT8I modules in the same system.