Siemens 6ES5373-1AA81 SIMATIC PLC Digital Input Module

Siemens 6ES5373-1AA81 is a 128 KB CMOS-EPROM memory module for the SIMATIC S5 family, specifically the 373 memory-module variant used to store the CPU’s program and related data. This non-volatile memory module is part of Siemens’ legacy 373 CMOS-EPROM lineup, offering 128 KB capacity alongside other capacities in the same family (e.g., 6ES5373-1AA41 with 32 KB and 6ES5373-1AA61 with 64 KB). The 6ES5373-1AA81 part number identifies the 128 KB CMOS-EPROM memory module intended for SIMATIC S5 controllers, ensuring compatibility with the S5 architecture’s memory interface. Designed for industrial automation environments that rely on Siemens S5 PLCs, this module provides persistent storage essential for program retention and data integrity in legacy systems.