Siemens 6ES5375-8LC21 SIMATIC S5 PLC Module Controller

Siemens 6ES5375-8LC21 is a SIMATIC S5 memory submodule (EEPROM) with 4 KB capacity, designed to provide non-volatile storage for legacy S5 PLCs. This 375-series memory module plugs into the S5 memory bus via the standard 40-pin front connector (type 490), ensuring compatibility with S5 CPUs and I/O modules that support the 375 EEPROM family. The 6ES5375-8LC21 designation identifies the 4 KB EEPROM option within the 6ES5375-8LCxx range. It serves as a dedicated memory submodule rather than an active processor, used to preserve program data and constants across power cycles. In practice, technicians install this submodule to replace worn memory or to expand non-volatile storage in older SIMATIC S5 installations, supporting continued operation of legacy automation equipment and easing recovery in service events. This part is commonly cataloged by Siemens and third‑party distributors as a spare memory module for S5-90U and S5-95U era systems, reflecting Siemens' long‑running strategy of modular memory within the S5 family. The 375 memory family includes variants with different EEPROM capacities, and 6ES5375-8LC21 specifically corresponds to a 4 KB EEPROM option, suitable for storing essential program data and constants used by the corresponding CPU modules in standard SIMATIC S5 configurations.