The Allen-Bradley 1756-CNBR, or ControlNet Bridge Redundancy, is an interface module used for communicating within a ControlNet Network. It is the same as the 1756-CNB but the biggest difference is that the 1756-CNBR has an additional ControlNet port, which will support redundant media. This module has 2 ControlNet BNC port while the 1756-CNB only has one, although both of them have 1 ControlNet RJ45 port.

Like the non-redundant module, the 1756-CNBR also controls scheduled data in conjunction to the Logix5550 Controller and bridges unscheduled data between the ControlLogix backplane and the ControlNet Network.

To prevent communication loss when a tap or trunkline is disconnected, a redundant ControlNet media can be used. For that connection, the only module you can use is the 1756-CNBR.

The technical specifications of this module are also similar to the non-redundant module. It can also handle up to 64 bidirectional scheduled and unscheduled connections with other ControlNet devices. Aside from that, up to 20 buffers for unconnected messages can be supported by the module. Also, this is the module needed if your application has 40 to 48 Logix communication connections per communication module and the communication rate is 5 megabytes per second. It also has 99 nodes available.

The current draw for the 1756-CNBR is 970 milliamperes at 5.1 Volts DC and 1.7 milliamperes at 24 Volts DC.

Before making your connection, make sure to check the tap drop cable for the label indicating the attached segment. This is to make sure that the tap connections will not be accidentally reversed. If not, these reversals will require troubleshooting and the status will be displayed incorrectly.

The Allen-Bradley 1756-CNBR is a ControlNet Bridge Module. This module is part of the ControlLogix product family that is used to interface a ControlLogix controller or implement Distributed I/O architecture via the high-speed ControlNet network. This module features Two (2) ControlNet ports, enabling connection to standard (simplex) and redundant ControlNet networks.

The 1756-CNBR supports transmission rate of 5Mbps, which is the standard transmission rate of the ControlNet protocol. It uses a quad shield RG-6 coaxial cable as trunk cable and established connection to the trunk cable with the use of ControlNet taps. This module supports 40-48 Logical communication connections and a maximum of 64 connections. The maximum number of nodes supported by the 1756-CNBR is 99 nodes.

The 1756-CNBR may be installed along the ControlLogix processor as a local communication module or to any distributed I/O rack as the head communication module. It is compatible with a variety of ControlLogix rack such as 1756-A4, 1756-A7, 1756-A10, 1756-A13, and 1756-A17. It may be installed to any available slot and only requires single slot in the chassis. It mat also be used with standard and redundant power supplies such as 1756-PA72/C, 1756-PA75/B, 1756-PB72/C, 1756-PB75/B, 1756-PC75/B, 1756-PH75/B and 1756-PA75R, 1756-PB75R, 1756-PSCA2, respectively.

The 1756-CNBR has additional One (1) Network Access Port (NAP) for local programming which is an 8-pin RJ45 physical port.

The 1756-CNBR communication module is backplane powered and draws 970 mA at 5.1VDC and 1.7 mA at 24VDC. It has a power dissipation of 5.1 Watts and Thermal dissipation of 17.4 BTU/hr.