> Someone asked what the difference between flash and eeprom really was...  I
> expected a flury of responses, but there haven't been any so far, so I'll
> take a shot at it.  As I understand it, the underlying technolgies are
> pretty substantially different (with flash being similar to eeprom
> technology, and EEPROM being more similar to RAM technology, I think.)
> However, the END USER difference is usually that EEPROM is erasable and
> re-writable on a byte-by-byte basis, while FLASH is only bulk erasable.
> I guess by labling the program memory "flash", a manufacturer does not
> have to provide byte erasability that my be difficult from any number
> of non-technology perspectives.

Sort of... from my perspective, Flash is closer to EPROM [single E] while
EEPROM is between EPROM and RAM in design.  Other properties:

[1] EEPROM is _usually_ byte-erasable though some older EEPROM chips were
    only device- or block-eraseable.

[2] EEPROM is _usually_ a higher-endurance technology, at least with regard
    to erase cycles (sometimes with Flash it's possible to successively clear
    bits until on the last cycle they're all erased; in this case, Flash's
    endurance can be pretty good).

[3] Many Flash chips offer substantially faster writes than EEPROM, but slower
    erase cycles.  I think AMD's 256x16 Flash device, for example, has a write
    cycle of about 10us [1000x faster than the 16C84 EEPROM] but an erase time
    of several seconds [300x slower than the 16C84 EEPROM].  Note that in many
    applications the erase time of a Flash device may not be a major issue
    since an erase cycle only has to be performed once for many bytes to be
    written.