Allen-Bradley 1756-DHRIO Digital High-Density Remote I O Module

The Allen-Bradley 1756-DHRIO is a Data Highway Plus (DH+) and Remote I/O bridge and scanner designed for ControlLogix systems. As a two-port module, it provides two DH+ ports and functions as a Remote I/O scanner on a DH+/RIO network, enabling data exchange between a ControlLogix controller and both DH+ devices and Remote I/O racks. It is designed to mount in a 1756 ControlLogix chassis and to interface with DH+ and Remote I/O networks via two channels and three terminal blocks. Rockwell describes the 1756-DHRIO as a DH+/RIO bridge that can connect legacy DH+ devices—such as PLC-5 or SLC 500 controllers—to a ControlLogix rack—facilitating data transfer and control signaling across networks. The module is part of Rockwell's ControlLogix I/O family and serves to integrate older DH+ networks with modern CLX systems. Note that Rockwell has announced the discontinuation of the ControlLogix DH Plus/RIO Communications Module line—including the 1756-DHRIO—effective December 31, 2024, with no further sales after that date.