Rockwell Automation 1738-AENT, Series B ArmorPOINT I/O Dual Port EtherNet/IP Adapters User Manual - Manual (Page 16)

6 Rockwell Automation Publication 1738-UM005A-EN-P - July 2013
Chapter 1 Overview of the 1738 ArmorPOINT I/O EtherNet/IP Adapter
Use of the Common
Industrial Protocol (CIP) The adapter uses the Common Industrial Protocol (CIP). CIP is the application
layer protocol specified for EtherNet/IP, the Ethernet Industrial Protocol, as well
as for ControlNet and DeviceNet networks. It is a message-based protocol that
implements a relative path to send a message from the producing device in a
system to the consuming devices.
The producing device contains the path information that steers the message along
the proper route to reach its consumers. Since the producing device holds this
information, other devices along the path simply pass this information; they do
not store it.
This has the following significant benefits:
• You do not need to configure routing tables in the bridging modules,
which greatly simplifies maintenance and module replacement.
• You maintain full control over the route taken by each message, which
enables you to select alternative paths for the same end device.
Understand the Producer/
Consumer Model The CIP producer and consumer networking model replaces the old source and
destination (master and slave) model. The producer and consumer model reduces
network traffic and increases speed of transmission. In traditional I/O systems,
controllers poll input modules to obtain their input status. In the CIP system,
input modules are not polled by a controller. Instead, they produce (multicast or
unicast) their data either upon a change of state (COS) or periodically.
Multicast is the default mode for version 17 Logix and earlier controllers and
unicast is the default for version 18 with multicast as a selectable option.
The frequency of update depends upon the options chosen during configuration
and where on the network the input module resides. The input module,
therefore, is a producer of input data, and the controller is a consumer of the data.
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