Allen-Bradley 1756-DHRIO Rio Communications Module

The Allen‑Bradley 1756‑DHRIO is a two‑channel DH+ (Data Highway Plus) and Remote I/O (RIO) communications module for ControlLogix backplanes. It bridges DH+ networks to a Rockwell Automation ControlLogix rack by providing two independently configurable channels (A and B) that carry DH+ traffic and function as a RIO scanner for Universal RIO networks, with three terminal blocks for wiring. This module enables DH+ messaging and RIO device access within a single chassis or across the DH+/RIO network, making it a practical option for integrating legacy DH+ devices and Remote I/O into modern ControlLogix systems. Configuration and topology are managed in Studio 5000/Logix Designer, where you define channel mode, node addresses, and I/O mapping. Common applications include bridging multiple DH+ devices to a single ControlLogix processor and enabling remote I/O blocks to be scanned by the controller, supporting gradual migration from legacy DH+/RIO architectures to contemporary ControlLogix setups. As of December 31, 2024, Rockwell Automation discontinued the 1756‑DHRIO; while new sales have ended, the module remains part of the historical ControlLogix ecosystem and may continue to operate in existing installations.