The CMOS bq4010/Y/LY is a nonvolatile 65,536-bit static RAM organized as 8,192 words by 8 bits. The integral control circuitry and lithium energy source provide reliable nonvolatility coupled with the unlimited write cycles of standard SRAM. The control circuitry constantly monitors the single supply for an out-of-tolerance condition. When VCC falls out of tolerance, the SRAM is unconditionally write-protected to prevent an inadvertent write operation.