Background To E²Proms

60 EE December 1988 BACKGROUND TO E"PROMS Memory chips with large storage capabilities invariably steal the limelight these days. There are, however, many interesting low- capacity devices available as well. One of these is the electrically erasable programmable read-only memory - E2PROM. Its low cost, versatility and ease of programming make this device an ideal component for many applications involving the permanent storage of, for instance, instrument configuration data. As an example of the operation and ap- plication of a typical E2PROM (or EEPROM), this article discusses the 256-bit Type NMC9306 from National Semiconductor. Readers of this maga- zine will recognize this device from the Microcontroller-driven power supply (Ref. 1), where it is used to for storage and retrieval of voltage and current set- tings associated with 3 user-selectable in- strument configurations. Basically, an E2PROM couples the non- volatily of an EPROM to the flexibility of a RAM. In this sense, it...