Description

The module often referred to as 1756-RIO is almost certainly the Allen-Bradley 1756-DHRIO (Data Highway Plus / Remote I/O Interface Module), a specialized communication card for the ControlLogix (1756) platform. Note: This is an Allen-Bradley (Rockwell Automation) product, NOT an ABB product. The 1756-DHRIO serves as a critical bridge, enabling modern ControlLogix processors to communicate with legacy Remote I/O (RIO) networks and Data Highway Plus (DH+) devices. This dual-port module allows plants to integrate older Allen-Bradley systems (like PLC-5. SLC 500. or older Bulk Remote I/O drops) into a modern ControlLogix architecture without replacing all field wiring and I/O racks. Engineered for robustness, the 1756-DHRIO is indispensable for facilities undergoing phased migrations or maintaining hybrid control systems where legacy RIO networks remain operational.

Application Scenarios

In a large automotive assembly plant, the main body shop utilizes a modern ControlLogix system for overall coordination, but the paint shop still relies on a decades-old Remote I/O (RIO) network connecting hundreds of discrete I/O blocks to control spray guns, conveyors, and ventilation. Replacing this entire network would cost millions and require months of downtime. Instead, engineers installed Allen-Bradley 1756-DHRIO modules in the new ControlLogix chassis. The 1756-DHRIO successfully scanned the existing RIO network, reading inputs and writing outputs to the old racks as if they were local I/O. When one of the original interface cards failed during a production surge, a swift replacement with a genuine 1756-DHRIO restored communication to the entire paint line within an hour, preventing a line stoppage that would have cost $50.000 per minute. This highlights the 1756-DHRIO’s vital role in protecting legacy investments while enabling modernization.