Allen-Bradley 1756-DHRIO Discrete High Density Digital IO Module

The Allen-Bradley 1756-DHRIO is a dual‑channel Data Highway Plus (DH+) remote I/O scanner/adapter module for ControlLogix backplanes. Each of its two channels can be configured in hardware and software to operate as a DH+ network interface or as a Remote I/O (RIO) scanner/adapter, enabling bridging between legacy DH+ devices or remote I/O racks and a ControlLogix chassis. The module occupies a single backplane slot and uses three terminal blocks to connect the two channels and the local programming interface, providing flexible wiring options in compact installations. As a remote I/O interface, it transfers digital I/O data between a DH+/RIO network and the main controller, supporting standard DH+ and Remote I/O data paths. The 1756‑DHRIO offers two independently configurable ports, allowing one channel to DH+ and the other to RIO if needed, which can simplify migrations from older I/O architectures to ControlLogix. This module is part of Rockwell Automation’s 1756 ControlLogix family. Note that Rockwell Automation announced the DH+/RIO module line, including the 1756-DHRIO, was discontinued and no longer available for sale as of December 31, 2024, so availability may be limited to remaining stock or used markets. Typical applications include connecting legacy DH+ devices or Remote I/O racks to a ControlLogix controller, enabling data exchange for discrete digital I/O and simple telemetry across DH+ or Remote I/O networks while preserving existing field devices and wiring.