Allen-Bradley 1756-DHRIO DH RIO Communication Module

The Allen-Bradley 1756-DHRIO is a two-channel DH+/Remote I/O communication module for ControlLogix systems that enables data exchange between a controller and DH+ devices as both a bridge and UR I/O scanner. Each channel (A and B) can be configured for DH+ network access or Universal Remote I/O mode, in which case the module acts as a UR I/O scanner on the network. DH+ data rates on the module reach up to 230.4 kbps, and each remote I/O channel supports up to 32 logical rack connections and 16 block transfer connections, allowing flexible I/O layouts across multiple remote racks. The 1756-DHRIO mounts in a 1756 backplane within a ControlLogix chassis and can route messages through multiple networks and chassis, bridging DH+/RIO domains to the controller. Note that Rockwell Automation discontinued the 1756-DHRIO as of December 31, 2024, making it a legacy solution best suited for existing installations rather than new designs.