Allen-Bradley 1756-DHRIO Digital Input Output Module

Allen-Bradley 1756-DHRIO is a DH+/RIO bridge/scanner module for Rockwell Automation's ControlLogix systems, providing two independent DH+ channels that connect a ControlLogix rack to DH+ remote I/O networks and Remote I/O devices. The module mounts in a 1756 backplane and uses three terminal blocks; it functions as both a DH+ bridge and a Remote I/O scanner, enabling the transfer of digital I/O data and supporting block-transfer communications to and from remote I/O modules. Each channel supports DH+ communications at 57.6 kbps, with RIO traffic configurable up to higher speeds (up to 230.4 kbps in some configurations), and it handles multiple remote I/O connections per channel. As of December 31, 2024, Rockwell Automation indicated this family of DH+/RIO communications modules has been discontinued and is no longer available new, though used units may still circulate. Common applications include migrating or interfacing legacy DH+ networks with modern ControlLogix controllers, enabling data exchange with DH+ devices and Remote I/O racks without a full network upgrade.