Rockwell Automation 1756-CFM ControlLogix Configurable Flowmeter Module - Manual (Page 23)

23 Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
Configurable Flowmeter Operation in the ControlLogix System 23
Configurable Flowmeter
Modules in a Local Chassis
CFM modules multicast their data periodically. Multicast frequency depends
on the options chosen during configuration and where in the control system
the module physically resides. The data consumer (an owner-controller) is
responsible for knowing that the format of the new data is integers.
Requested Packet Interval (RPI)
This configurable parameter instructs the module to multicast its channel and
status data to the local chassis backplane at specific time intervals.
The RPI instructs the module to multicast the current contents of its
on-board memory when the RPI expires, (i.e. the module does not update its
channels prior to the multicast) as shown in this figure.
IMPORTANT
You set the RPI value during the initial module
configuration and can adjust it the controller is in Program
mode.
The minimum RPI is determined by channel usage. For
each channel using High Resolution Frequency mode, add
5 ms to the minimum RPI. For each channel using
Totalizer Mode, add 50 ms to the minimum RPI.
For example, if one channel uses High Resolution
Frequency mode and the other goes unused, the minimum
RPI = 5 ms. If one channel uses High Resolution
Frequency mode and the other uses Totalizer mode, the
minimum RPI = 55 ms.
On-Board Memory
Status Data
Flowmeter 0
Flowmeter 1
Ch 0
Ch 1
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