The DS1248 1024K NV SRAM with Phantom Clock is a fully static nonvolatile RAM (organized as 128K words by 8 bits) with a built-in real-time clock. The DS1248 has a self-contained lithium energy source and control circuitry, which constantly monitors VCCfor an out-of-tolerance condition. When such a condition occurs, the lithium energy source is automatically switched on and writes protection is unconditionally enabled to prevent garbled data in both the memory and real-time clock.