Protection circuit for storage of volatile data

摘要

A protected memory circuit for use with an electronic data system includes a memory element such as a shift register, and memory control or lock means to selectively control enablement of the memory element for read/write operations. A separate power supply which may be a charged capacitor is used to power the memory and memory lock circuits in case of a power interruption in the main system with which the memory is being used, so that volatile data can be stored for re-use by the main system after the main power is restored. The lock includes a counter and a gate for inhibiting clock pulses to the memory element until a predetermined number of control pulses have been received to initiate a read/write operation. At all other times the clock input is blocked or clamped to prevent spurious signals or power surge transients from altering the stored data.