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Allen-Bradley 1756-CN2R ControlLogix ControlNet Communication Module (Redundant Media)
1. Product Overview
The 1756-CN2R is a ControlNet redundant-media bridge module in Allen-Bradley's (Rockwell Automation) ControlLogix® Bulletin 1756 family. It installs in any ControlLogix chassis slot, exchanges data with the Logix controller over the backplane, and provides two BNC coax ports (Channel A and Channel B) to connect to a redundant ControlNet trunk.
ControlNet is Rockwell's high-speed deterministic fieldbus based on CIP, running at a fixed 5 Mbps in producer/consumer mode for real-time I/O and peer communications. The CN2R uses dual-coax redundant media: Channel A and Channel B each run an independent quad-shield RG6 trunk. Both channels operate in parallel; if one cable or connector fails, the module automatically switches to the other, keeping the network up — suited to critical, high-availability applications.
The module supports up to 99 ControlNet nodes and 131 Logix communication connections. A front-panel USB 1.1 (Series B) port and network/module status LEDs are provided. It draws 5.1V DC/1.3A and 24V DC/3mA from the backplane.
2. Specifications
表格
| Item | Specification |
|---|---|
| Manufacturer | Allen-Bradley / Rockwell Automation |
| Brand series | ControlLogix (Bulletin 1756) |
| Catalog number | 1756-CN2R |
| Product type | ControlNet redundant-media bridge module |
| Network | ControlNet (CIP fieldbus) |
| Baud rate | 5 Mbps (fixed) |
| ControlNet ports | 2× BNC (Channel A + Channel B, redundant media) |
| Cable | 1786-RG6 quad-shield RG6 coaxial |
| Nodes | Up to 99 |
| Connections | Up to 131 |
| Redundant media | Supported (dual A/B parallel, auto-switch on fault) |
| Configuration port | USB 1.1 (Series B receptacle) |
| Backplane supply | 5.1V DC @ 1300mA; 24V DC @ 3mA |
| Power dissipation | 6.6 W (22.5 BTU/hr) |
| Isolation | 30V continuous (basic insulation), 500V AC/60s hi-pot ControlNet-to-system |
| Slot width | 1 slot |
| Mounting | Any ControlLogix chassis slot |
| Operating temperature | 0 to +60 °C |
| Enclosure rating | Open-style (panel-mount in enclosure) |
| Status indication | Module and network status LEDs |
| Configuration software | Studio 5000 Logix Designer, RSLinx Classic, RSNetWorx for ControlNet |
| Tap cable | 1786-TC1 ControlNet tap |
| Suffix note | R = redundant media; K = conformal coating; XT = extended temp (−25 to +70°C, 1756-CN2RXT) |
5. Model Information
- Catalog number (ordering number): 1756-CN2R
- Product description: Allen-Bradley ControlLogix ControlNet redundant-media bridge module, dual BNC coax, 5 Mbps, 131 connections.
- Official catalog description: ControlLogix redundant media ControlNet bridge module, 2 BNC coax ports, 5 Mbps, up to 131 connections.
- Material number note: 1756-CN2R is the official Rockwell ordering number. 1756 = ControlLogix platform, CN = ControlNet, 2 = second-generation bridge, R = redundant media. Suffix K = conformal coating; XT = extended-temperature version (1756-CN2RXT). If you have questions on single vs. redundant media, node count or connections, please contact us by email.
- Series features:
- Backplane-mount ControlLogix ControlNet bridge
- Dual BNC coax ports, A/B redundant media
- Fixed 5 Mbps deterministic real-time communication
- Up to 99 nodes, 131 Logix connections
- Auto-switch redundant media for high availability
- USB 1.1 configuration port
- 5.1V/1.3A backplane current, 6.6W power
- Studio 5000 / RSNetWorx configuration
- Related products in series: 1756-CN2 (single channel, 1 BNC, 1100mA), 1756-CNBR (legacy, 64 connections), 1756-CN2RXT (extended-temp redundant, −25 to +70°C), 1756-CN2K (single-channel conformal coating)
- Matching products: ControlLogix chassis (1756-A series), ControlLogix power supply (1756-P series), ControlLogix 5570/5580 controllers, 1786-RG6 coax cable, 1786-TC1 tap, 1787 connectors/terminators
- Official documents: 1756-IN074 "ControlLogix ControlNet Communication Modules Installation Instructions"; 1756-TD003 "1756 ControlLogix Communication Modules Specifications"; RSNetWorx for ControlNet documentation
6. Why Choose Us
- Exact model match: We verify supply against your full catalog number 1756-CN2R, distinguishing CN2R (redundant dual port) from CN2 (single port), CNBR (legacy 64 connections) and CN2RXT (extended temp) to avoid wrong shipment.
- Authorized channel supply: Allen-Bradley / Rockwell Automation products supplied through regular channels, with product documentation available on request.
- Selection support: We help confirm redundant-media wiring, node addressing, connection count and chassis/power/controller slot matching.
- Delivery & after-sales: Quotation, lead-time confirmation and order follow-up provided; for any parameter questions or alternative options, please contact us by email.
7. FAQ
Q1: What is the 1756-CN2R?
A: It is a ControlNet redundant-media bridge module for the ControlLogix 1756 system, mounting in a chassis slot and connecting via two BNC coax ports to a redundant ControlNet network for real-time I/O, HMI and peer controller communications.
Q2: What does "redundant media" mean?
A: The module has Channel A and Channel B BNC ports, each connected to an independent RG6 coax trunk. Both channels run in parallel; if one cable or connector fails, the module automatically switches to the other without network interruption.
Q3: What is the baud rate, and how many nodes/connections?
A: ControlNet runs at a fixed 5 Mbps, supporting up to 99 nodes and 131 Logix communication connections.
Q4: How does it differ from the 1756-CN2?
A: The 1756-CN2 is the single-channel version with one BNC port, no redundant media, drawing 1100mA; the 1756-CN2R is the dual-BNC redundant-media version drawing 1300mA.
Q5: Does it need external power?
A: No. It draws 5.1V DC/1.3A and 24V DC/3mA from the ControlLogix backplane; power dissipation is 6.6W.
Q6: What cable and tap are used?
A: 1786-RG6 quad-shield RG6 coax cable, connected via 1786-TC1 ControlNet taps, with 75Ω terminators at both ends of the trunk. Suffix K is conformal coating and XT is extended temperature. Please email us to confirm.
