Allen-Bradley 1775-MED Error Correcting Memory Module

Allen-Bradley 1775-MED is an error-correcting RAM memory module for the PLC-3 family of controllers. It provides 128K words of ECC-protected memory to store ladder logic, data tables, and other program data, improving reliability by detecting and correcting single-bit errors on the backplane. The 1775 memory family spans 16K (ME4), 32K (ME8), 64K (MEA), and 128K (MED) capacities, illustrating the range of RAM options used in PLC-3 installations. This plug-in module installs in the PLC-3 processor chassis as a dedicated RAM option that supports the era’s backplane architecture for stable memory in industrial control environments.