What is Non Volatile SRAM, NV RAM memories, nvSRAM, Non Volatile SRAM

 MX29F Series 4-Mbit (512 K x 8) 70 ns 5 V Surface Mount Flash Memory - PLCC-32

https://www.futureelectronics.com/p/semiconductors--memory--RAM--nvram--quantum-trap-nvsram/mx29f040cqi-70g-macronix-6159320