Publication 1756-PM004C-EN-P - October 2009 11
Communicate with I/O Modules Chapter 1
Communication Format
The communication format that you choose determines the data structure for
the tags that are associated with the module. Many I/O modules support
different formats. Each format uses a different data structure. The
communication format that you choose also determines:
•
Direct or Rack-Optimized Connection.
• Ownership.
Direct or Rack-Optimized Connection
The Logix5000 controller uses connections to transmit I/O data. These
connections can be direct connections or rack-optimized connections.
Term Definition
Direct connection A direct connection is a real-time, data transfer link between the controller and an I/O
module. The controller maintains and monitors the connection with the I/O module. Any
break in the connection, such as a module fault or the removal of a module while under
power, sets fault bits in the data area associated with the module.
Rack-optimized
connection
For digital I/O modules, you can select rack-optimized communication. A rack-optimized
connection consolidates connection usage between the controller and all the digital I/O
modules in the chassis (or DIN rail). Rather than having individual, direct connections for
each I/O module, there is one connection for the entire chassis (or DIN rail).
A direct connection is any
connection that does not
use the Rack Optimization
Comm Format.
Rack-Optimized Connection
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