The 1756-DNB is a single-slot DeviceNet scanner and bridge module for the Allen‑Bradley ControlLogix chassis platform, manufactured by Rockwell Automation. It acts as the primary interface between the high-speed ControlLogix backplane and a DeviceNet industrial fieldbus network, enabling the ControlLogix controller to scan, exchange I/O data, and communicate with DeviceNet slave devices including remote I/O blocks, variable frequency drives, motor starters, sensors, valve banks, barcode readers and other ODVA-compliant field instruments. This module remains an active lifecycle product and is widely deployed in packaging, material handling, automotive assembly, food and beverage, and general factory automation where DeviceNet field wiring is already installed.

As both scanner and gateway, the 1756-DNB polls configured nodes on the DeviceNet network and maps all input, output and diagnostic data directly into the ControlLogix tag database. It supports multiple message types including cyclic I/O, change-of-state, strobed and polled messaging, giving engineers flexible ways to balance network load and update rates. The module can be fitted in any empty slot inside a standard 1756 ControlLogix chassis, either local to the controller or in a remote chassis reachable via ControlNet or EtherNet/IP, making it easy to integrate DeviceNet islands into larger NetLinx automation architectures.

The 1756-DNB supports three selectable DeviceNet baud rates: 125 kbps, 250 kbps and 500 kbps. Each speed carries a maximum allowed trunk cable length: 500 m at 125 kbps, 250 m at 250 kbps, and 100 m at 500 kbps. It can manage up to 64 network nodes on one DeviceNet trunk, with a practical working limit of 63 active slave devices. The module also supports DeviceNet Safety, so it can connect and exchange safe I/O with certified safety devices on the same bus, supporting safety interlock workflows on production lines. A built-in USB network access port allows technicians to plug in a configuration laptop without tapping into the main trunk, for commissioning, node addressing, firmware updates and live diagnostics.

Configuration and scan list setup for the 1756-DNB rely on RSNetWorx for DeviceNet, while tag mapping and controller programming are completed in RSLogix 5000 / Studio 5000 Logix Designer. Users build the scan list to define which slave nodes are active, allocate I/O word space, and set data exchange directions. The module supports up to 124 input words and 123 output words for mapped field data, which is sufficient for most mid-sized DeviceNet networks. It works across the full ControlLogix controller family, including 5550, 5570 and 5580 series, subject to matching firmware revisions and connection resource planning.

On the front panel, the 1756-DNB includes a four-character alphanumeric diagnostic display plus dedicated LED indicators for module run status, network activity, bus faults and communication errors. The display shows node address, active faults, duplicate node conflicts, bus off conditions and backplane errors, greatly speeding up troubleshooting during commissioning or unplanned downtime. Common issues visible from the module include bus short circuits, power failures on the DeviceNet trunk, disconnected taps, faulty slave nodes and mismatched baud rate settings.

For electrical specifications, the 1756-DNB draws 400 mA at 5.1 VDC from the ControlLogix backplane, with a typical power dissipation of 3.5 W. The DeviceNet side runs on 11–25 V DC SELV power and draws up to 60 mA from the fieldbus supply. It provides basic isolation between the DeviceNet network and the ControlLogix backplane, with continuous rated isolation voltage of 50 V and withstand tested at 853 V AC for one minute. The module is rated for standard industrial cabinet operating temperatures and carries UL, CE and relevant global industrial certifications.

Typical application scenarios for the 1756-DNB include new builds that reuse existing DeviceNet field devices, retrofitting older PLC systems to ControlLogix, expanding packaging and conveyor lines, adding variable drives over DeviceNet, and stocking spare modules for plants with established DeviceNet infrastructure. Many integrators pair the 1756-DNB with other ControlLogix communication cards such as 1756-CN2R for ControlNet and EtherNet/IP modules to combine multiple fieldbus layers inside one control system. When sourcing, buyers can select new factory sealed, surplus open-box or fully tested refurbished units; refurbished stock will complete full backplane communication, network scanning, fault simulation and LED testing before shipment. Always confirm firmware compatibility and total network node count before deployment to avoid bandwidth or connection overflow.

Key technical highlights of 1756-DNB:

• Brand: Allen‑Bradley (Rockwell Automation)
• Catalog number: 1756-DNB
• Product type: DeviceNet Scanner / Bridge Module
• Platform: ControlLogix 1756 chassis
• Max nodes: 64 total nodes, up to 63 active slaves
• Baud rates: 125 kbps / 250 kbps / 500 kbps
• I/O mapping: Up to 124 input words, 123 output words
• Auxiliary port: USB NAP for direct programming access
• Safety: Supports DeviceNet Safety devices
• Backplane current: 400 mA @ 5.1 VDC
• Power dissipation: 3.5 W
• Configuration software: RSNetWorx for DeviceNet, Studio 5000 / RSLogix 5000
• Mounting: Single slot in any standard ControlLogix chassis
• Diagnostics: 4‑digit alphanumeric display + multi-status fault LEDs
• Lifecycle: Active, not discontinued
• Common paired modules: 1756-CN2R, 1756-EN2T, 1756-IF16, 1756-OB16E
  

  1756-DNB