Allen-Bradley controllogix 1756-L55M12, User Manual

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Publication 1756-UM001G-EN-P - January 2007
56 Place, Configure, and Monitor I/O Modules
I/O Connections
A Logix5000 system uses connections to transmit I/O data.
Additional Resources
For additional information, consult these publications:
•
Logix5000 Controllers Common Procedures Programming
Manual, publication 1756-PM001
•
Logix5000 Controllers Design Considerations Reference Manual,
publication 1756-RM094
Connection Type Description
Direct 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 between the controller and the I/O module. Any break in the connection,
such as a module fault or the removal of a module while under power, causes the controller to set fault status bits in
the data area associated with the module.
Typically, analog I/O modules, diagnostic I/O modules, and specialty modules require direct connections.
Rack-optimized For digital I/O modules, you can select rack-optimized communication. A rack-optimized connection consolidates
connection usage between the controller and all of the digital I/O modules on a rack or DIN rail. Rather than having
individual, direct connections for each I/O module, there is one connection for the entire rack or DIN rail.