Support for rack-optimized and direct connections – Rockwell Automation 1738-AENT, Series B ArmorPOINT I/O Dual Port EtherNet/IP Adapters User Manual User Manual
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Rockwell Automation Publication 1738-UM005A-EN-P - July 2013
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Overview of the 1738 ArmorPOINT I/O EtherNet/IP Adapter Chapter 1
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 for Rack-optimized
and Direct Connections
The I/O adapter 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
eight I/O modules. If you use a rack-optimized connection to transfer the data,
you only need a single connection – the connection to the I/O adapter.
ET-AP005
, for more information on connections.
IMPORTANT
Although rack-optimized connections offer an efficient way to use
resources, there are a few limitations on their use:
• You can use only rack-optimized connections to send data to and
from digital I/O modules. Analog or speciality I/O requires direct
connections.
• 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-optimized connection, a direct connection to that
digital I/O module is required.