Allen-Bradley 1771-DCM Direct Communication Module

The Allen-Bradley 1771-DCM Direct Communication Module (catalog number 1771-DCM) is a PLC-5 era module designed to enable direct data exchange between supervisory and local processors over the Remote I/O protocol. This dedicated communication module fits into a PLC-5 Remote I/O backplane and coordinates data transfers across the Remote I/O network, helping to streamline cross-processor communications within a PLC-5 installation. Typical applications include linking a supervisory controller to one or more PLC-5 local processors to share input/output data and status information without relying on separate polling interfaces. The module is part of the 1771 ecosystem, using standard Allen-Bradley backplane connections and Remote I/O wiring common to PLC-5 installations. Rockwell Automation documentation presents the 1771-DCM as the Direct Communication Module for establishing direct processor-to-processor communication within Remote I/O networks, a configuration frequently encountered in legacy automation setups. As a legacy module, the 1771-DCM is typically referenced in historical Rockwell literature and current distributor catalogs for PLC-5 systems, where it provides a dedicated conduit for cross-processor data exchange within Remote I/O networks.