Rockwell Automation 1738-AENTR, Series A 1734 POINT I/O and 1738 ArmorPOINT I/O 2 Port Ethernet/IP Adapter User Manual - Manual (Page 14)

6 Rockwell Automation Publication 1734-UM014B-EN-P - June 2013
Chapter 1 About the Adapters
The controller also produces data for other controllers to consume. The
produced and consumed data is accessible by multiple controllers and other
devices over the EtherNet/IP network. This data exchange conforms to the
producer and consumer model.
Specify the Requested
Packet Interval (RPI)
The Requested Packet Interval or RPI is the update rate specified for a particular
piece of data on the network. The RPI can be specified for the adapter and
include all of the I/O modules in the I/O system (using a rack-optimized
connection) or specified for a particular module (using direct connection).
When you add a module or an adapter to the I/O configuration of a controller,
you must enter the RPI as a parameter. This value specifies how often to produce
the data for that device. For example, if you specify an RPI of 50 ms, it means that
every 50 ms the device should send its data to the controller and the controller
should send the consumed (output) data to the device.
Use RPIs only for devices that exchange data. For example, a ControlLogix
EtherNet/IP bridge module in the same chassis as the controller does not require
an RPI, because it is not a data-producing member of the system. Its use is only as
a bridge to remote racks.
Support of Rack-optimized
and Direct Connections The I/O adapters supports both direct and rack-optimized connections. A direct
connection is a real-time data transfer link between the controller and the module
occupying the slot that the configuration data references.
Direct I/O connections occur at a cyclic rate specified by the RPI during
configuration. A rack-optimized connection is a grouping of data from one or
more digital I/O modules into a single block of data sent over a single connection
at the same data rate.
Analog, safety, and speciality modules cannot participate in the rack-optimized
connection; these modules require a direct I/O connection.
Rack-optimized connections reduce the total number of connections needed to
transfer data when using many digital I/O modules in a system. The following
example illustrates the benefit of rack-optimized connections.
Assume you set up a system that contains eight digital I/O modules interfaced to
an adapter. If you use direct connections to transfer data to each of the these I/O
modules, you need eight connections to transfer all of the data, one to each of the