Siemens 6ES5374-1KH21 Programmable Logic Controller Module

Siemens 6ES5374-1KH21 is a memory card for the SIMATIC S5 family, a short-design, 5V-only Flash-EPROM module with a capacity of 256 KB. It provides non-volatile storage for program code, configuration data, and runtime parameters, enabling critical control data to be retained during power interruptions. The 6ES5374-1KH21 is designed to be inserted into S5 memory card slots and is commonly paired with the IM308-C interface module (PROFIBUS-DP master) for use in 115U/135U/155U systems; Siemens notes that the memory card must be ordered separately. The 256 KB capacity suits compact control programs and configuration data typical of older SIMATIC S5 deployments. This memory card is part of Siemens' line of S5 memory cards, enabling flexible storage management and program/data backup without altering the CPU's core memory. The 1KH21 variant is identified by this specific part number and is widely sold as a spare part by Siemens and third-party distributors. Its short-design form factor is optimized for the S5 memory card slots used in legacy 374-series memory architectures. When replacing or upgrading S5 memory, ensure you select the matching 6ES5374-1KH21 card to preserve compatibility with your backplane and IM308-C module.