The Rockwell Automation 1756-CNB or ControlNet Bridge module is an interface module used for interfacing a ControlLogix rack to ControlNet network. Compared to the Rockwell Automation 1756-CNBR module, the 1756-CNB is used in standard, non-redundant configurations. This module is perfect if the user applications have 40 to 48 Logix communication connections per communication module. It has a communication rate of 5 Megabytes per second and it has 99 nodes available. The 1756-CNB module handles 2 things: namely, the control of I/O data when it is used with a Logix5550 controller for scheduled data and for unscheduled data, bridging data between the ControlLogix backplane and the ControlNet Network. Make sure that the path information is correct, in order to properly route the messages being received.

Up to 64 bi-directional connections with other ControlNet devices can be supported by the 1756-CNB module. It can be a mix of both scheduled and unscheduled connections. However, the number of supported connections also depends on the network configuration. If an application needs more connections, the users can add another 1756-CNB module, but they must make sure to do it in the same chassis and on the same network as the first module. It can also support up to 20 buffers for unconnected messages. It also has 2 ports - 1 ControlNet BNC port and 1 ControlNet RJ45 port. The operator needs to set the module’s node address switches first when installing the 1756-CNB module. They can select a unique node address from 01 to 99. The users can then use the module as a standalone control module by using 1 set of modules or as a redundant control setup by using identical pairs of modules (partners). Note that when using redundant control, the node address switches should have the same node address. The 1756-CNB current draw at 5.1 Volts DC is 970 milliamperes and 1.7 milliamperes if the current draw is at 24 Volts DC. Its power dissipation is rated at 5.14 Watts.