Rockwell Automation 1734-ACNR POINT I/O ControlNet Adapter User Manual - Manual (Page 24)

Publication 1734-UM008B-EN-P - August 2005
3-4 Plan to Use Your Adapter
Rack Connections
A rack connection supports a group of modules. The 1734-ACNR
supports five instances of the rack object that provide the ability to
communicate I/O data from all discrete I/O modules in the 1734 bus
via one connection pair. The rack object contains both I/O and
diagnostic status.
The rack connection specifies the same fixed size of I/O data for all
modules, starting at slot 0 (adapter).
Multiple rack connections are limited to a maximum of 5 rack
connections. Rack connections are defined using RSLogix5000
software and can be of either of the following types:
• rack optimization, or
• listen only optimization
Assume you have set up a system that contains 8 discrete I/O modules
interfaced to a 1734-ACNR adapter. If you use direct connections to
transfer data to each of these I/O modules, you need 8 connections to
transfer all of the data, one to each of the 8 I/O modules. If you use a
rack-optimized connection to transfer the data, you need only a single
connection - the connection to the 1734-ACNR adapter.
IMPORTANT
Slot 0 is reserved for the adapter. The adapter is not
a member in the rack.
IMPORTANT
Although rack optimized connections offer an
efficient way to use resources, there are a few
limitations on their use:
• You can only use rack optimized connections to
send data to and from discrete I/O modules.
Analog I/O and specialty I/O require direct
connections.
• Rack optimized connections can contain I/O data
and status information only.
• All data is sent at the same time at the API rate of
the adapter.