User manual

Publication ENET-UM001I-EN-P - January 2010 83
Control I/O Chapter 6
Choosing a 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 maintain
s 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
connec
tion
For digital I/O modules, you c
an 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
IMPORTANT
If you use various 1756 EtherNet/IP communication modules in
a remote chassis, such as a 1756-ENBT with a 1756-EN2T, do
not use the rack-optimized communication format with this
remote chassis. If you must use the rack-optimized
communication format with a remote 1756 chassis, put the
1756-EN2T and 1756-ENBT modules in a separate remote
chassis.