Allen-Bradley 1756-DHRIO RIO Interface Module

Allen-Bradley 1756-DHRIO is a Data Highway Plus/Remote I/O interface module for ControlLogix backplanes, providing two DH+ channels (A and B) to bridge a DH+ network with a ControlLogix processor and Remote I/O devices. It supports DH+ messaging between devices on a DH+ network and enables data exchange with Remote I/O scanners, effectively allowing legacy DH+ installations to integrate with modern ControlLogix systems. The module is installed in a 1756 I/O chassis and acts as the bridge between the DH+ network and the ControlLogix backplane, enabling communication with DH+ devices such as PLC-5 or SLC 500-era equipment that still use DH+. Rockwell’s documentation identifies the 1756-DHRIO family as the DH Plus/RIO communication interface module for ControlLogix, and as of December 31, 2024, Rockwell announced the DH Plus/RIO module line is discontinued and no longer available for sale.