Allen-Bradley 1756-CN2RXT B
Allen-Bradley 1756-CN2RXT B
Allen-Bradley 1756-CN2RXT B
Allen-Bradley 1756-CN2RXT B
Allen-Bradley 1756-CN2RXT B
Allen-Bradley 1756-CN2RXT B
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1756-CN2RXT/B

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The 1756-CN2RXT/B is a ControlLogix‑XT ControlNet interface module with firmware rev20.013, supporting 128 standard connections (131 total) and requiring RSLogix 5000 v16.0+ and RSLinx 2.55+.
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Technical specifications for 1756-CN2RXT/B

  • Manufacturer:
    Allen-Bradley
  • Part Number:
    1756-CN2RXT/B
  • Product Family:
    ControlLogix
  • Firmware Revision:
    20.013
  • RSLogix 5000 Compatibility:
    Version 16.0 or later
  • RSLinx Classic Compatibility:
    Version 2.55 or later (otherwise module won't display)
  • Maximum Connections:
    131 total (3 reserved for redundancy → 128 standard)
  • Incompatible Hardware:
    1756‑CN2x/A (do not attempt firmware upgrade)
  • Firmware Source:
    Same as 1756‑CN2R/B module
  • Browsing Methods:
    USB port or network connection
  • Corrected Anomalies:
    Rack‑optimized fault mode error; Hold Net Resource timing; Power‑up red OK indicator
  • Weight:
    0.4 kg
  • Estimated shipping dimensions:
    17.4x3.5x14.1cm
  • Tariff Code:
    8517795000
  • Country of origin:
    USA
  • Place of shipment:
    Xiamen, Fujian, China
By purchasing this item, you agree to the Terms & Conditions, ApterPower is not an authorized distributor for listed manufacturers or tradenames and therefore the manufacturer's warranty does not apply. All our products come with ApterPower's 1-year warranty.

More Information

Overview Manuals Specifications Application Performance Application Scenarios

Features:

  • XT extreme temperature rating,Designed for harsh, extended‑temperature environments.
  • 128 usable ControlNet connections,Out of 131 total, with 3 reserved for redundancy.
  • Corrected rack-optimized fault handling,Outputs now go to Fault mode instead of Program mode.
The 1756‑CN2RXT B is built for ControlLogix‑XT systems, operating reliably in harsh environments where standard modules fail. It withstands wider temperature ranges and corrosive conditions, making it ideal for oil refineries, outdoor installations, and extreme climate zones. Always pair it with an XT‑rated chassis such as the 1756‑A5XT or 1756‑A7LXT.

The 1756‑CN2RXT B provides 131 total connections, but three are permanently reserved for redundant control. This leaves 128 connections for standard I/O and communication. The reserved connections always appear "in use" even when idle, so do not be alarmed. Plan your system knowing you have exactly 128 available connections.

Before firmware rev20.013, a rack‑optimized 1756‑CN2RXT B would send outputs to Program mode states instead of Fault mode during a communication fault. This could cause unexpected machine behavior. The corrected firmware now sends outputs to Fault mode as intended. If unable to upgrade, use direct connections as a temporary workaround.

The 1756-CN2RXT/B Allen-Bradley Interface Module may still be available for purchase and support from Apter Power beyond End-Of-Life (EOL) by the manufacturer (OEM).

Allen-Bradley 1756-CN2RXT/B Interface Module Manuals, Datasheets, Drivers, Link Important Notice: Other accessories, manuals, cables, calibration data, software, etc. are not included with this equipment unless listed in the above stock item description. All prices are shown in USD.
Allen-Bradley 1756-CN2RXT/B Interface Module Specs

General

  • Manufacturer Allen-Bradley
  • Model 1756-CN2RXT/B
  • Condition New Original ready stock
  • Product Family 1756‑CN2R/B,1756‑CN2/B,1756‑CN2RXT/D
Important Notice: Other accessories, manuals, cables, calibration data, software, etc. are not included with this equipment unless listed in the above stock item description. All prices are shown in USD.
  • Energy and Resources: Such as oil and gas extraction platforms, wind turbines, and mining environments.
  • Shipping and Marine Engineering: Suitable for shipbuilding and offshore facilities, addressing challenges of high humidity and salt spray.
  • Critical Infrastructure: Used in monitoring systems with extremely high requirements for communication stability and redundancy, such as water treatment and power dispatching.
  • Wide Temperature Range: Operating temperature range extended to -25°C to +70°C (-13°F to 158°F), with improved heat dissipation and ventilation design.
  • High Connectivity: Supports up to 131 connections (128 for user use, 3 reserved for redundant control), suitable for large distributed I/O systems.
  • Data Determinism: ControlNet provides highly deterministic and repeatable data transmission, ensuring that critical control commands (such as motion control or high-speed I/O) arrive within the scheduled time.
  • Redundant Recovery and Stability: Series B improves recovery time after multiple connection interruptions and reduces state errors such as NET ERR through internal firmware optimizations.
  • High Availability Control System: Symmetrical 1756-CN2RXT modules are installed in redundant racks as communication bridges between master and slave chassis. When the master communication cable fails, the module automatically switches to the backup channel without interrupting operation.
  • Remote I/O Bridging: In remote, high-temperature environments far from the central control room, this module transmits remote I/O data across the ControlNet network back to the control center.
  • Local Maintenance in Harsh Environments: Series B modules are equipped with an industrial-grade USB interface (replacing the older NAP interface), allowing maintenance personnel to directly connect to a laptop for temporary programming or diagnostics on-site.
Description
The 1756-CN2RXT/B requires RSLogix 5000 version 16.0 or later and RSLinx Classic version 2.55 or later. Without RSLinx 2.55, the module will not display properly in the network. This firmware revision 20.013 corrects several anomalies, including a communication fault when configured as rack‑optimized.

A corrected anomaly for the 1756-CN2RXT/B involved outputs going to Program mode instead of Fault mode. The previous workaround was using a direct connection. Another fix addressed an error on 'Hold Net Resource' requests, and a power‑up issue where the OK indicator stayed red due to inaccurate chassis size detection.

The 1756-CN2RXT/B supports a maximum of 131 connections, but three are always reserved for redundant control. Thus only 128 connections are available for standard use. Do not attempt to upgrade a 1756‑CN2x/A module with firmware for the 1756-CN2RXT/B; ControlFLASH will show a severe incompatibility warning.

To browse the 1756-CN2RXT/B in RSLinx software version 2.55+, access it via USB port or network connection. Use ControlFLASH to update firmware, downloading the same firmware as the 1756‑CN2R/B module. In RSLogix 5000, add it as a 1756‑CN2R/B module and assign the correct slot number.
Revisions

Revision Part #

Also known as

1756-CN2RXT Ser A
1756-CN2RXT/A, Series A, Rev A
1756-CN2RXT Ser B
1756-CN2RXT/B, Series B, Rev B
Alternative Names
1756‑CN2R/B 1756‑CN2/B 1756‑CN2RXT/D 1756‑CN2R/D
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FAQS

The following is a list of questions commonly asked by our customers. Please contact us if you have a question about our process that is not answered below.
Why can't I see the 1756‑CN2RXT B in RSLinx?
You need RSLinx Classic version 2.55 or later. Earlier versions will not display the module properly. Also verify you are using RSLogix 5000 version 16.0 or later. Update your software before attempting to browse or configure the 1756‑CN2RXT B.
What was fixed regarding rack‑optimized mode on the 1756‑CN2RXT B?
Previously, during a communication fault, outputs would go to Program mode states instead of Fault mode. Firmware rev20.013 corrects this. If you cannot upgrade, use direct connections for each I/O module instead of rack‑optimized as a workaround.
Can I put 1756‑CN2RXT B firmware into an older 1756‑CN2x/A module?
No. The 1756‑CN2RXT B firmware revision 20.13 is not compatible with 1756‑CN2x/A hardware. ControlFLASH will display a severe incompatibility warning. Do not attempt this update or you may brick the module.