Allen-Bradley 1756-CNB/E, User Manual

Page: 70 / 186

Publication 1756-UM523F-EN-P - December 2006
70 Configure and Program the Controller
Configure Communications
A redundant system requires some specific configuration choices for
successful communications. Use this section to perform these
redundancy tasks:
•
Configure I/O
•
Configure produced tags
•
Configure message (MSG) instructions
•
Configure tags for an HMIConfigure I/O
For any outputs that require a bumpless switchover:
•
put those outputs in the highest priority task.
•
configure only that task at the highest priority.
Configure Produced Tags
If you want a controller in another chassis to consume a tag from the
redundant controller, use a comm format of None. In the I/O
configuration of the consuming controller, select a comm format of
None for the remote CNB module (the CNB that is physically in the
redundant chassis).
IMPORTANT
For each module in your system, make sure that the requested
packet interval (RPI) is less than or equal to 375 milliseconds. If
you use a larger RPI, the controller could lose its connection
with the module during a switchover. This could cause outputs
to change state.
IMPORTANT
During a switchover, the connection for tags that are consumed
from a redundant controller may time out.
•
The data does not update.
•
The logic acts on the last data that it received.
After the switchover, the connection reestablishes and the data
begins to update again.
IMPORTANT
If
If you set the remote CNB module to a comm format other than
None, you will receive module fault 16#000C in RSLogix5000.
This fault signifies a service request error due to an invalid
mode or status during a service request.