Rockwell Automation 1794-AENTR_AENTRXT FLEX I/O Dual Port EtherNet/IP Adapter Modules - Manual (Page 12)

Publication 1794-UM066A-EN-P - February 2012
4 Overview of FLEX I/O and Your Redundant EtherNet/IP Adapter Module
The controller can also produce data for other controllers to consume. The
produced and consumed data is accessible by multiple controllers over the
EtherNet/IP network. This data exchange conforms to the producer/consumer
model.
Specifying the Requested
Packet Interval (RPI) The 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
communicating through it (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 50ms the device
should send its data to the controller or the controller should send its data to the
device.
RPIs are only used for devices that produce 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; it is used only as
a bridge to remote racks.
Support of Rack Optimized
and Direct Connections The 1794-AENTR and 1794-AENTRXT adapters support both direct and rack
optimized connections. A direct connection is a real-time data transfer link
between the controller and the device that the configuration data references.
Direct connection messaging occurs at a cyclic rate specified by the RPI during
configuration. A rack optimized connection is a grouping of data from more than
one I/O module into a single block of data sent over a single connection at the
same data rate.
Rack optimized connections reduce the total number of connections needed to
transfer data when using many I/O modules in a system. The following example
illustrates the benefit of rack optimized connections.
Assume you have set up a system that contains 8 discrete 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 8 connections to transfer all of the data, one to each of