Rockwell Automation 1756-OF8H ControlLogix HART Analog I/O Modules - Manual (Page 42)

42 Rockwell Automation Publication 1756-UM533C-EN-P - February 2011
Chapter 3 ControlLogix Module Operation
Requested Packet Interval (RPI)
This configurable parameter also instructs the module to multicast its channel
and status data to the local chassis backplane.
The requested packet interval instructs the module to multicast the current
contents
of its on-board memory when the requested packet interval expires (the
module does not update its channels prior to the multicast).
Figure 2 -
If the real time sample value is less than or equal to the requested packet interval,
each multicast of data from the module has updated channel information. In
effect, the module is only multicasting at the real time sample rate.
If the real time sample value is greater than the requested packet interval, the
module multicasts at both the real time sample rate and the requested packet
interval rate. Their respective values dictate how often the owner-controller
receives data and how many multicasts from the module contain updated channel
data.
On-board Memory
Status Data
Channel Data
Channel Data
Channel Data
Channel Data
Channel Data
Channel Data
Ch 0
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Timestamp
41362
IMPORTANT The requested packet interval value is set during the initial
module configuration using RSLogix 5000 software. This value
can be adjusted when the controller is in Program mode.