Allen Bradley 1756-CN2R Redundant Interface Module

The AB 1756-CN2R is a redundant ControlNet communication module designed for ControlLogix systems, providing high-performance, fault-tolerant communication across two independent ControlNet channels. With support for up to 128 Logix connections and dual active ports, this module enables seamless redundancy and high availability in mission-critical industrial control networks.

Engineered for robust distributed control, the 1756-CN2R installs into any standard 1756 chassis and offers deterministic, scheduled communication between Logix controllers and ControlNet-enabled devices such as I/O, drives, and HMIs. It’s ideal for high-reliability applications where uptime and communication resilience are essential.

Technical Specifications

Model: 1756CN2R
Series: ControlLogix
Type: Redundant ControlNet Communication Module
Logix Connections: 128
Max Network Nodes: 100 ControlNet devices
Communication Channels: 2 (redundant dual ports)
Mounting Type: 1756 Chassis Slot
Application: High-availability distributed control, safety systems, motion control, and process automation

Electrical & Interface Specifications

Communication Protocol: ControlNet
Network Speed: 5 Mbps (standard ControlNet speed)
Connector Type: BNC Coaxial (one per channel)
Redundancy: Yes – Dual active channels for automatic failover
Backplane Communication: Via 1756 backplane
Backplane Current Draw: Approx. 500 mA @ 5.1V DC
Compatible Software: RSNetWorx for ControlNet, Studio 5000
Power Supply: Supplied via ControlLogix chassis backplane

Mechanical Specifications

Width: 35 mm
Height: 145 mm
Depth: 140 mm
Mounting: ControlLogix rack (standard 1756 chassis)
Form Factor: Slot-based modular
Weight: Approx. 300 g
Housing: Industrial-grade module enclosure

Environmental Specifications

IP Rating: IP20 (when installed in panel/chassis)
Operating Temperature: 0…60 °C
Storage Temperature: -40…85 °C
Humidity: 5% to 95%, non-condensing
Vibration/Shock Resistance: Complies with IEC 60068-2 standards
Certifications: CE, cULus, RoHS
Explosion Safety (Gas/Dust): Not rated

Compliance & Communication

ControlNet Supported: Yes (dual channel redundancy)
Data Highway / EtherNet/IP / DeviceNet / MODBUS / PROFIBUS / TCP/IP: Not supported
Other Bus Systems: Supported via ControlNet architecture
Diagnostic Features: Built-in status LEDs and RSNetWorx diagnostics
Failover Capability: Automatic switching between active and backup channels
Max Scheduled Connections: Fully supported via ControlNet configuration tools

Key Features & Benefits

✅ Dual Redundant Channels – Ensures continuous communication with failover capability

✅ High-Capacity Connectivity – Supports 128 Logix connections and up to 100 ControlNet nodes

✅ Reliable Real-Time Data – Deterministic, scheduled data transmission for critical systems

✅ Chassis-Based Form Factor – Compact 35 mm width fits into standard 1756 racks

✅ Software Integration – Fully supported by RSNetWorx and Studio 5000 environments

✅ Ideal for High Availability Systems – Perfect for safety, batch, and process control networks

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