The DS2227 combines voltage monitoring circuitry with lithium-backed memory in a flexible architecture that can be accessed as 128k x 32, 256k x 16, or 512k x 8 bits. Using precise comparators, the DS2227 monitors incoming Vcc for an out-or-tolerance condition. When such a condition occurs, the internal lithium energy source is automatically switched on and write protection is unconditionally enabled to prevent data corruption. While the DS2227 is used like a standard static RAM, it can be flexibly configured by virtue of separate read, write, and chip-select bits for each of the four memory banks. Dallas' nonvolatile memory chips are known throughout the industry for low-power consumption. They render data nonvolatile for greater than 10 years in the absence of power, greater than the useful like of the associated equipment. * Memory with flexible architecture: * 128k x 32 * 256k x 16 * 512k x 8 * NV circuitry transparent to/independent of host * Automatic write protection circuitry * Separate chip-enables for access by byte, word, or long word * Access times: 70ns, 100ns, or 120ns * Unlimited write cycles * Equal read/write cycle times * JEDEC-standard 72-position SIMM connection * Lithium source with freshness seal * Operating ranges: * 5V±10% tolerance * 0°C to 70°C