Allen-Bradley 1756-CNB - Page 175

Publication 1756-UM523F-EN-P - December 2006
Series B ControlNet Bridge Modules 175
Loss of Communication
Restriction Description
Communication Loss When Bridging
Through a Series B ControlNet Bridge
Module.
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.
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
N
B
/
B
L
5
5
M
x
C
N
B
S
R
M
Redundant Chassis Pair
D
H
R
I
O
Remote I/O
1756-CNB/B or 1756-CNBR/B Module
Remote Chassis
IMPORTANT
On the first switchover after you download a project to the controller, you may
temporarily lose communications with these devices
Other Modules