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Rockwell Automation Publication 1789-UM002K-EN-P - January 2015
Chapter 2
What is the SoftLogix System?
Connections for I/O Modules
The SoftLogix system uses connections to transmit I/O data. These connections
can either be direct connections or rack-optimized connections.
To conserve the number of connections that are available, place digital
I/O modules together in the same location and use a rack-optimized connection.
To choose a rack-optimized connection, choose a ‘rack-optimized’ option for the
communication format when you add the communication device and
I/O modules to the controller project in the Logix Designer application.
If you have analog I/O modules, or want a direct connection to specific
I/O modules, you do not have to create the rack-optimized connection to the
communication device. To use direct connections to I/O modules, choose ‘none’
for the communication format of the communication device.
Total Connection
Requirements
The SoftLogix controller supports 250 connections. Each 1784-PCICS
ControlNet communication card supports 128 total connections, 127 of which
can be scheduled. Do not configure more connections than the controller can
support. Use this table to tally ControlNet connections.
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.
Rack-optimized
For digital I/O modules, you can choose 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).
Table 3 - Connections
Connection Type
Device Quantity
Connections Per
Device
Total Connections
Remote EtherNet/IP communication device (such as a 1794-AENT or 1756-ENBT
module):
•
Configured as a direct (none) connection
•
Configured as a rack-optimized connection
0
1
Remote I/O device over the EtherNet/IP network (direct connection)
1
Produced and consumed tag:
•
Produced tag and one consumer
•
Each additional consumer
1
1
Consumed tag
1
Cached message
1
Total
