Allen-Bradley 1788-CN2DN System-Ready Network Bridge for ControlLogix Architecture

Allen-Bradley 1788-CN2DN System-Ready Network Bridge for ControlLogix Architecture

The Allen-Bradley 1788-CN2DN is a purpose-engineered ControlNet-to-DeviceNet Linking Device designed to serve as a critical communication bridge within layered industrial automation architectures. Rather than functioning as a standalone component, the 1788-CN2DN occupies a strategic position in the network layer of a ControlLogix-based control system, enabling seamless data exchange between the high-speed ControlNet backbone and the device-level DeviceNet field bus. This integration capability makes it an indispensable element for engineers designing scalable, redundant, and maintainable process control systems across manufacturing, power distribution, petrochemical, water treatment, and mining applications.

In a complete ControlLogix system architecture, the 1788-CN2DN operates between the controller backplane layer and the field device layer. The ControlLogix chassis — typically housing a 1756-L7x or 1756-L8x series CPU module alongside 1756-PA75 or 1756-PB75 power supply modules — communicates upstream via ControlNet using the 1756-CNB or 1756-CNBR communication module. The 1788-CN2DN then bridges this ControlNet segment to a DeviceNet network where distributed I/O devices, variable frequency drives, smart sensors, and actuator control blocks reside. This architecture eliminates the need for direct backplane I/O modules for every field device, dramatically reducing cabinet footprint and wiring complexity while improving system modularity.

From a signal flow perspective, the 1788-CN2DN acts as a scheduled and unscheduled data router. Scheduled ControlNet traffic — carrying deterministic I/O data from field devices such as 1794-ADNX FLEX I/O DeviceNet adapters or PowerFlex 40 and PowerFlex 755 drives — is mapped through the linking device and presented to the ControlLogix controller as if it were local I/O. Unscheduled messaging supports explicit message commands for configuration, diagnostics, and parameter reads from connected DeviceNet nodes. This dual-mode communication capability ensures that both real-time control loops and maintenance-level device interrogation can coexist on the same physical infrastructure without performance degradation.

System redundancy is a key consideration in critical process environments. When paired with a 1756-CNBR redundant ControlNet bridge module and a 1756-RM2 redundancy module, the 1788-CN2DN can be incorporated into a fully redundant ControlLogix architecture. In such configurations, the linking device maintains DeviceNet network continuity even during controller switchover events, ensuring that field devices — including 1734-ADN POINT I/O DeviceNet adapters and distributed motor control nodes — remain online and responsive. This capability is particularly valued in continuous process industries where unplanned downtime carries significant operational and safety consequences.

Installation and commissioning of the 1788-CN2DN follows standard Allen-Bradley network configuration procedures using RSNetWorx for DeviceNet and RSNetWorx for ControlNet software tools. Node addressing, network scan list configuration, and I/O mapping are performed through RSLogix 5000 or Studio 5000 Logix Designer, ensuring full compatibility with existing ControlLogix programming environments. The device supports standard DeviceNet baud rates of 125 Kbps, 250 Kbps, and 500 Kbps, and ControlNet data rates up to 5 Mbps, providing flexibility for both legacy and modern network segments.

Long-term maintenance efficiency is enhanced by the 1788-CN2DN’s diagnostic transparency. Network health indicators, node fault reporting, and connection status LEDs allow maintenance engineers to rapidly identify communication faults without requiring specialized test equipment. When integrated with a 1756-ENBT or 1756-EN2T EtherNet/IP bridge module at the supervisory layer, remote diagnostic access via FactoryTalk View or FactoryTalk AssetCentre becomes possible, enabling predictive maintenance workflows and reducing mean time to repair across geographically distributed plant assets.

Inventory availability and supply chain continuity are critical factors for long-term system support. ZYPLC maintains stock of the 1788-CN2DN alongside complementary components including 1756-CNB, 1756-CNBR, 1794-ADNX, 1734-ADN, and 1756-DNB modules, ensuring that system integrators and plant maintenance teams can source complete network layer assemblies from a single supplier. All units are tested prior to shipment and covered by a 12-Month Warranty, providing documented assurance of functional integrity for both new installations and system expansion projects.

Architecture Specification Table

Coordinated Control System Design

The 1788-CN2DN achieves its full architectural value when deployed as part of a coordinated ControlLogix system. A typical system configuration begins with a 1756-L74 or 1756-L75 ControlLogix CPU installed in a 1756-A10 or 1756-A17 chassis, powered by a 1756-PA75 AC power supply. The 1756-CNB ControlNet bridge module connects the chassis to the ControlNet trunk cable, over which the 1788-CN2DN receives scheduled I/O data requests from the controller. On the DeviceNet side, the linking device manages communication with 1794-ADNX FLEX I/O adapters carrying analog and digital I/O modules, 1734-ADN POINT I/O DeviceNet adapters for distributed terminal-level I/O, and PowerFlex 40 or PowerFlex 755 variable frequency drives for motor speed control. In redundant architectures, the 1756-CNBR module replaces the standard 1756-CNB, and the 1756-RM2 redundancy module coordinates controller switchover without disrupting DeviceNet network traffic managed by the 1788-CN2DN. At the supervisory level, a 1756-EN2T EtherNet/IP module provides connectivity to the plant SCADA or DCS layer, completing a fully integrated, multi-layer automation architecture.

Application in Layered Automation Systems

In discrete manufacturing environments, the 1788-CN2DN enables centralized ControlLogix controllers to manage large populations of DeviceNet-connected devices — including smart sensors, barcode readers, and pneumatic valve manifolds — across assembly lines and material handling systems without expanding the controller backplane. In power distribution and substation automation, the device facilitates integration of DeviceNet-based protection relays and motor control centers into ControlNet-based supervisory architectures, supporting IEC 61850-aligned communication strategies. Petrochemical and refinery applications benefit from the 1788-CN2DN’s ability to maintain deterministic communication with field instruments and valve positioners in hazardous area installations, where minimizing field wiring and junction boxes is a safety and cost priority. Water and wastewater treatment facilities use the linking device to connect distributed pump control panels and flow measurement devices to centralized ControlLogix systems managing treatment process sequences. In mining and metals processing, the 1788-CN2DN supports high-availability architectures for conveyor drive systems, crusher controls, and process weighing stations, where network reliability directly impacts production throughput and safety system response times.

Architecture Engineering FAQ

Q1: Is the 1788-CN2DN compatible with both ControlLogix and SoftLogix platforms, and what software tools are required for configuration?
The 1788-CN2DN is fully compatible with Allen-Bradley ControlLogix and SoftLogix controller platforms. Configuration requires RSNetWorx for DeviceNet for node commissioning and scan list setup, RSNetWorx for ControlNet for network scheduling, and RSLogix 5000 or Studio 5000 Logix Designer for I/O mapping and controller program integration. No additional hardware configuration tools are required beyond standard Allen-Bradley network commissioning software.

Q2: Can the 1788-CN2DN be used in a redundant ControlLogix architecture, and does it maintain DeviceNet communication during controller switchover?
Yes. When the ControlLogix system is configured with a 1756-CNBR redundant ControlNet bridge and a 1756-RM2 redundancy module, the 1788-CN2DN continues to manage DeviceNet network communication transparently during controller switchover events. DeviceNet nodes remain online and I/O data integrity is maintained throughout the redundancy transition, making this configuration suitable for critical process control applications where uninterrupted field device communication is a system requirement.

Q3: What does the 12-Month Warranty cover, and how does ZYPLC support long-term architectural maintenance for systems using the 1788-CN2DN?
The 12-Month Warranty provided by ZYPLC covers functional defects identified under normal operating conditions within twelve months of shipment. All units undergo functional testing prior to dispatch. For long-term architectural maintenance, ZYPLC maintains inventory of the 1788-CN2DN and associated ControlNet and DeviceNet components, enabling rapid replacement sourcing for system integrators and plant maintenance teams. Technical pre-sales support is available to assist with compatibility verification, system architecture review, and spare parts planning for both new installations and legacy system expansions.

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