Overview
The Allen-Bradley 1756-CNB Series D is a ControlLogix communication module designed to bridge a ControlLogix rack to a ControlNet industrial network. This single-slot communication adapter provides high-speed, non-redundant connectivity for distributed I/O systems and inter-controller communication. The 1756-CNB is ideal for control applications requiring reliable data transfer between multiple ControlLogix controllers and ControlNet nodes without redundancy.
Key Features
- Non-redundant ControlNet bridge – Single coaxial media connection for standard ControlNet deployments
- 5 Mbps communication rate – High-speed deterministic data transfer across the ControlNet network
- 64 bidirectional connections – Supports up to 64 simultaneous communication paths with other ControlNet devices
- 99 maximum nodes – Accommodates large distributed automation systems on a single ControlNet segment
- 40–48 logical connections – Flexible ControlLogix communication connection assignments
- Dual communication ports – One BNC coaxial connector and one NAP (Network Access Protocol) RJ-45 8-pin connector with shield
Technical Specifications
- Series: D (F/W Rev. 5.5 and later)
- Communication Protocol: ControlNet
- Data Rate: 5 Mbps
- Power Supply (5.1V DC): 970 mA
- Power Supply (24V DC): 1.7 mA
- Power Dissipation: 5.14 W
- Isolation Voltage: 30V Continuous
- Maximum Nodes: 99
- Bidirectional Connections: 64 maximum
- Logix Connections: 40–48 per module
- Connectors: 1 × BNC (coaxial), 1 × NAP RJ-45 (8-pin shielded)
- Mounting: Chassis slot (any available slot)
- Enclosure: Open-style module
- Redundancy Support: Non-redundant only (Series D)
Typical Applications
- Distributed I/O architectures with multiple ControlLogix racks across a ControlNet network
- Inter-controller messaging and data synchronization in multi-PLC systems
- Remote device bridging to main ControlLogix control system via ControlNet highway
- Standard (non-redundant) production lines and process control systems
- Scheduled and unscheduled data bridging between ControlLogix backplane and ControlNet
Compatibility & Replacements
Compatible With
- ControlLogix chassis (all models)
- Logix5550, Logix5560, Logix5570, and Logix5580 controllers
- Allen-Bradley ControlNet modules, interface cards, and partner modules
- Flex I/O ControlNet adapters
- PLC-5 and SLC ControlNet systems (via bridging)
- POINTIO distributed I/O nodes on ControlNet
- RS-Linx classic and RS-Linx gateway software
- Studio 5000 (Logix Designer) programming environment
Replaces / Drop-In Replacement For
- Earlier revisions of 1756-CNB Series D
- Legacy 1756-CNB Series C (with firmware compatibility verification)
Works With
- Studio 5000 (Logix Designer) engineering software
- RS-Logix 5000 programming platform
- RS-Linx network communication driver
- ControlNet protocol (ISO/IEC 61158-3-1)
- Allen-Bradley Redundancy releases 8, 11, 13, and 15 (Series D only)
- ControlLogix chassis backplane communications
- MSG (Message) instructions for unscheduled data transfers
