Abstract: MOS Control circuitry for incorporation on a microcomputer IC chip for assuring adequate power to maintain the data in an associated static random access memory. A rechargeable battery provides standby power, and the voltage level of the battery is compared with the microcomputer V.sub.cc supply. Whenever V.sub.cc drops below a predetermined level, such as the standby battery voltage level, the circuitry disconnects the V.sub.cc from the memory input power and replaces it with standby battery power. When V.sub.cc is returned to the system, a gate applies a trickle charge to the battery.