Rockwell Automation 1794-L34 FlexLogix Controller System User Manual - Manual (Page 57)

Publication 1794-UM001G-EN-P - January 2007
Place, Configure, and Monitor I/O 57
I/O connections
A Logix5000 system uses connections to transmit I/O data. A
connection can be:
Connections for local and extended-local I/O modules
The FlexLogix controller automatically assigns one rack-optimized
connection for the local DIN rail and one rack-optimized connection
for the extended-local DIN rail. You then configure each I/O module
on a DIN rail to either use that rack-optimized connection or to use a
direct connection. The rack-optimized connection for each DIN rail
exists whether or not you configure the I/O modules to use that
rack-optimized connection.
The rack-optimized connection lets you organize all the digital I/O
modules on one DIN rail into one connection to the controller. Or you
can choose to configure each I/O module to have a direct connection
to the controller. Analog I/O modules must have a direct connection
to the controller.
It is not as critical to manage the number of connections for local and
extended-local I/O modules as it is for remote devices because the
controller supports a direct connection for each possible local and
extended-local I/O device.
Connection: 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 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).