The DS1270W 16Mb nonvolatile (NV) SRAMs are 16,777,216-bit, fully static, NV SRAMs organized as 2,097,152 words by 8 bits. Each NV SRAM has a self-contained lithium energy source and control circuitry that constantly monitors VCC for an out-of-tolerance condition. When such a condition occurs, the lithium energy source is automatically switched on and write protection is unconditionally enabled to prevent data corruption. There is no limit on the number of write cycles that can be executed, and no additional support circuitry is required for microprocessor interfacing.