Abstract: This application note discusses theory of operation and application of NV SRAMs such as the DS1220, DS1225, and DS1230. First it discusses NV RAM module construction, with an overview of the battery, controller and SRAM that is used in a typical device. Application information regarding interconnects to popular 8-bit Motorola and Intel bus structures is shown in block diagram form. Answers to common questions regarding issues found during the design, test, manufacture, and use of NV SRAMs in electronic systems is explained in detail. Information on some older and obsolete parts is discussed with recommendations on pin-for-pin replacements with more contemporary devices