Overview
The Allen-Bradley 1756-CNB is a ControlLogix ControlNet bridge module engineered to provide a non-redundant interface between the Logix backplane and a ControlNet network for distributed I/O and flexible communication routing. This single-slot chassis module bridges scheduled and unscheduled traffic, allowing ControlLogix controllers to communicate across ControlNet networks with distributed devices, other automation nodes, and HMI/SCADA systems. The 1756-CNB Series D is a proven solution for industrial automation applications requiring medium-scale network integration without redundancy requirements.
Key Features
- 5 Mbps ControlNet communication rate for responsive distributed I/O and messaging
- Supports up to 99 nodes on the ControlNet network with flexible node address selection (01–99)
- Manages up to 64 bidirectional connections including scheduled and unscheduled traffic
- Non-redundant design with one BNC connector (ControlNet media) and one RJ-45 NAP interface
- Integrated diagnostics: front-panel status display showing connection state, node address, module name, and error counters
- Fits any standard ControlLogix chassis as a single-slot module
Technical Specifications
- Network Protocol: ControlNet (5 Mbps)
- Connectors: 1× BNC (ControlNet), 1× RJ-45 NAP (8-pin shielded)
- Maximum Nodes: 99 on ControlNet
- Logix Connections: 40–48 communication connections per module
- Maximum Connections: 64 bidirectional (scheduled and unscheduled)
- Power Supply: 24 VDC (backplane-powered)
- Power Consumption: ~5.14 W at 5.1 V DC; 1.7 mA at 24 V DC
- Operating Temperature: −40 to +70 °C (−40 to +158 °F)
- Isolation Voltage: 30 V continuous
- Dimensions: 1.5″ W × 6.0″ H × 5.5″ D (3.8 cm × 15.2 cm × 14.0 cm)
- Weight: 0.48 lbs (0.22 kg)
- Mounting Style: Single-slot ControlLogix chassis
Typical Applications
- Connecting ControlLogix controllers to legacy or existing ControlNet distributed I/O networks
- Bridging communication between ControlLogix and non-redundant ControlNet devices in manufacturing, packaging, and process control systems
- Expanding ControlNet networks for mid-scale automation architectures without redundancy
- Facilitating scheduled scan data and unscheduled messaging between backplane-mounted and remote ControlNet nodes
- System upgrades and retrofit applications in facilities with established ControlNet infrastructure
Compatibility & Replacements
Compatible With
- ControlLogix processor platforms (Logix5550, Logix5560, CompactLogix with ControlNet gateway)
- ControlLogix chassis (1756 series) as local or distributed I/O head module
- Rockwell Studio 5000 (RSLogix 5000, Studio 5000) programming software
- RSNetWorx network configuration and diagnostic software
- ControlNet physical media (ControlNet taps, trunk line, drop cable)
- Distributed ControlLogix I/O modules and remote adapter devices
Replaces / Drop-In Replacement For
- 1756-CNB (all earlier revisions including Series A, B, C)
- 1756-CNB/D modules in equivalent applications
- Note: For redundant ControlNet requirements, refer to the 1756-CNBR module instead
Works With
- Studio 5000 (RSLogix 5000) for I/O configuration and messaging parameter setup
- RSNetWorx for network management, node address assignment, and bandwidth planning
- ControlNet protocol for deterministic, real-time scheduled I/O communication
- EtherNet/IP integration (via EtherNet/IP-to-ControlNet gateways)
