Allen-Bradley 1734 - Connections; Mixing Rack-Optimization, Enhanced Rack-Optimization, and Direct Connections

10 Rockwell Automation Publication 1734-UM018D-EN-E - September 2017
Chapter 1 Overview of the 1734 POINT I/O EtherNet/IP Adapter
Analog, safety, and specialty modules cannot participate in the rack-optimization
connection; these modules require an enhanced rack-optimization or direct I/O
connection.
Enhanced rack-optimization connections reduce the total number of
connections needed to transfer data when using many digital and analog, or
specialty modules in a system.
Rack-optimization 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-optimization 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
eight I/O modules. If you use a rack-optimization connection to transfer the data,
you only need a single connection – the connection to the I/O adapter.
See the EtherNet/IP Embedded Switch Technology Application Guide,
publication ENET-AP005
, for more information on connections.
Mixing Rack-optimization, Enhanced Rack-optimization, and
Direct Connections
You can mix communication formats for different I/O modules communicating
through the same adapter. I/O modules set up to use rack optimization or
enhanced rack-optimization communicate at the rate of the RPI configured for
the adapter. I/O modules configured for direct communication communicate at
their own individual RPIs and ignore the rack-optimization RPI.
IMPORTANT
Although rack-optimization and enhanced rack-optimization connections
offer an efficient way to use resources, there are a few limitations on
their use:
• You can use only rack-optimization or enhanced rack-optimization
connections to send data to and from digital I/O modules.
• Safety modules, IO link modules, and third-party I/O modules can
not participate in enhanced rack-optimization connections.
• Enhanced rack-optimization does not support a listen only
connection. Do not use enhanced rack-optimization if your
application requires a connection for monitoring.
• All data is sent at the same time as the RPI rate of the I/O adapters.
If the update rate required for a digital module is different from the
RPI of the rack-optimization or enhanced rack-optimization
connection, a direct connection to that I/O module is required.