Siemens 6ES5375-0LD21 Programmable Logic Controller Module

Siemens 6ES5375-0LD21 memory submodule for SIMATIC S5 expands the system RAM by 16 KB within the MS375 RAM memory family, enabling larger or more complex programs and extended data handling in legacy PLC installations. As a plug-in RAM module, it interfaces with compatible S5 CPUs and sits in the memory slot used by the MS375 memory architecture, providing a straightforward upgrade path without replacing the CPU or backplane. This memory extension is particularly valuable for retrofitting aging Siemens S5 lines or preserving production lines that rely on RAM-based subsystems, allowing longer program memory, more data registers, and improved runtime performance within a familiar automation stack. With 16 kilobytes of RAM on board, the 6ES5375-0LD21 remains a commonly referenced part in Siemens spare-part catalogs and vendor listings for S5 memory expansions, maintaining compatibility across multiple S5 configurations and helping extend the life of legacy control networks.