Allen-Bradley 1756-CNB User Manual page 175

Restriction
Communication Loss When Bridging
Through a Series B ControlNet Bridge
Module.
Loss of Communication
Description
You could temporarily lose communication with a remote chassis if you use both these modules in
the chassis:
• 1756-CNB/B or 1756-CNBR/B module.
• 1756-DHRIO module that is connected to a remote I/O network.
Redundant Chassis Pair
L
5
5
M
x
Remote Chassis
C
N
B
/
B
On the first switchover after you download a project to the controller, you may
IMPORTANT
temporarily lose communications with these devices
The loss of communication occurs on the first switchover after you download the project to the
redundant controller.
• You lose communication with the remote chassis and any devices to which you were bridging
via the chassis, such as the remote I/O modules.
• During the communication loss, the I/O modules go to their configured state for a
communication fault.
• The communication loss is temporary. Communications restore themselves.
To prevent this situation, use 1756-CNB/D/E or 1756-CNBR/D/E modules.
C S
N R
B M
1756-CNB/B or 1756-CNBR/B Module
D
H
Other Modules
R
I
O
Remote I/O
Publication 1756-UM523F-EN-P - December 2006
Series B ControlNet Bridge Modules 175