Allen-Bradley 1756-DHRIO ControlLogix Communication Module

The Allen-Bradley 1756-DHRIO is a DH+/RIO remote I/O communication interface module for Rockwell's ControlLogix platform. It enables a ControlLogix CPU to communicate with remote I/O devices across a Data Highway Plus network, acting as a DH+ remote I/O scanner that bridges legacy DH+ devices with modern ControlLogix controllers. The module installs in a 1756 ControlLogix chassis and is configured via Rockwell software to participate in a remote I/O network, enabling data exchange with remote racks and devices on the DH+ bus. Typical uses include linking older DH+ peripherals to a ControlLogix system, extending I/O reach without replacing existing devices. Rockwell has discontinued sales of the 1756-DHRIO and related modules, with the discontinuation effective December 31, 2024; for new designs, consider migration paths to current DH+/RIO alternatives or to more modern communication options, while existing installations can continue to operate with supported firmware where available.