Publication 1756-UM001G-EN-P - January 2007
Place, Configure, and Monitor I/O Modules 61
Add 1756 I/O at Runtime
With RSLogix 5000 programming software, version 16, you:
• can only add 1756 I/O modules to the Controller Organizer at
runtime.
• can remotely add the 1756 I/O modules to the local chassis via
the unscheduled portion of a ControlNet network.
• can remotely add the 1756 I/O modules to the local chassis via
the unscheduled portion of an EtherNet/IP network.
ControlNet I/O Considerations
When you add ControlNet I/O at runtime:
• remember that the ControlNet I/O modules you add can be
added to existing rack-optimized connections or added as direct
connections.
You cannot create new rack-optimized connections when
adding ControlNet I/O modules at runtime.
• disable the Change of State (COS) feature on digital input
modules because it can cause inputs to be sent more quickly
than the RPI.
• dedicate one ControlNet network to I/O communication only.
On the dedicated I/O network, make sure there is:
– no HMI traffic.
– no MSG traffic.
– no programming workstations.
• RPIs faster than 25 ms for unscheduled modules will overload
the 1756-CNB or 1756-CNBR communication module, so:
– use a NUT if 10 ms or more.
– keep the SMAX and UMAX values as small as possible.
• you can add I/O modules until you reach:
– 75% utilization of the 1756-CNB or 1756-CNBR
communication module.
– a utilization increase of 1...4% for each I/O module you add,
depending on the RPI.
– 48 connections on the 1756-CNB or 1756-CNBR
communication module.
– < 350,000 bytes as the remaining unscheduled bandwidth on
the ControlNet network.
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