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PLC, I/O & HMI
1756-CNB
Allen-Bradley
Allen-Bradley 1756-CNB sourcing reference. Send the complete nameplate details and required quantity for review.
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Reference details
- Manufacturer / brand
- Allen-Bradley
- Model / reference
- 1756-CNB
- Series / type
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- Condition
- Confirm with inquiry
- Quantity
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- Lead time
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Product information
Product Overview
The 1756-CNB is the ControlNet bridge module for the ControlLogix 1756 platform, linking the chassis backplane to a ControlNet coaxial network (BNC connector, 1786-RG6 quad-shield cable, 5 Mbps). Official Rockwell data lists 40…48 Logix communication connections (64 maximum supported) and up to 99 nodes on the network segment. A separate NAP RJ45 port serves the programming tool. Rockwell’s lifecycle status is Discontinued — ControlNet has been superseded by EtherNet/IP across the Rockwell portfolio.
Technical Specifications (Official Rockwell Data)
| Product family | ControlLogix communication module |
|---|---|
| Network | ControlNet (coax) |
| Interface | 1 × ControlNet BNC; 1786-RG6 quad-shield coaxial cable |
| Transmission rate | 5 Mbps |
| Logix communication connections | 40…48 (64 maximum supported) |
| Nodes per network segment, max | 99 |
| Programming/service port | 1 × NAP RJ45 (1786-CP cable) |
| Current draw | 970 mA @ 5.1 V DC, 1.7 mA @ 24 V DC |
| Power dissipation | 5.1 W (17.4 BTU/h) |
| Operating temperature | 0…60 °C (32…140 °F) |
| Vibration / shock | 2 G @ 10…500 Hz; 30 G operating |
| Lifecycle status (Rockwell) | Discontinued; repair options available |
Lifecycle Status & Availability
Rockwell officially lists the 1756-CNB as Discontinued. ControlNet itself is a legacy network: new Rockwell architectures run deterministic control over EtherNet/IP (CIP Motion/CIP Safety), and the 1756-CNB appears only in the installed base. Repair options remain available. This makes the CNB a typical spare-part purchase for plants whose deterministic control loops still ride on coaxial ControlNet trunks.
Typical Applications
- Spares for plants running deterministic ControlNet segments (interlocks, drive groups) installed in the 1990s–2000s
- Revision-matched replacements where migrating a segment to EtherNet/IP needs a scheduled outage
- Bridging legacy 1771/1794 remote I/O that hangs off ControlNet taps
Related & Compatible Models
Related modules: 1756-CN2/CN2R (higher-connection ControlNet bridges, also discontinued), 1756-DNB (DeviceNet scanner), and the EtherNet/IP successors 1756-EN2T/EN2TR/EN4TR for networks being modernized. Planning a ControlNet-to-EtherNet/IP migration typically pairs bridge replacement with controller and I/O-adapter changes — state your end goal in the quotation request.
Requesting a Quotation
Send the complete catalog number with series letter and firmware revision (nameplate photo preferred), the required quantity, and whether your ControlNet segment uses redundant media (CNB vs CN2R family matters). Availability, condition and pricing are confirmed individually.
Frequently Asked Questions
Is ControlNet still supported by Rockwell?
The ControlNet network and 1756-CNB are discontinued. Rockwell’s current deterministic network is EtherNet/IP. Existing ControlNet segments continue to operate, but replacement hardware comes from remaining stock — verify availability per request.
What is the difference between CNB and CN2?
The 1756-CN2 generation raised connection capacity and node performance over the original CNB. Both are discontinued now. Match your installed module type when ordering spares.
Can I migrate ControlNet to EtherNet/IP without rewriting everything?
Often yes at the network level — many ControlNet roles (remote I/O, drives) map onto EtherNet/IP adapters, but scheduled change management is required. Share your segment layout in the quotation request if you want a migration-oriented quote.
Which cable does the CNB use?
1786-RG6 quad-shield coaxial cable with BNC taps per official Rockwell data, plus a 1786-CP cable on the NAP port for programming.
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