> I think with Flash you can't re-write anything, you need to erase
> it first. Some let you erase just a single byte, others a page, still
> others the whole chip. Does that make it easier or harder?

The 29C040A does an automatic erase before write, so that's
covered. It also has a small sector size of 256 bytes (2048 of
them), which is about all you can load into an F877. As far as I
can see, the smallest sector size in a "large" Flash memory is
64 bytes. It's a read-modify-write operation - you have to load the
sector into the PIC, modify it and then write it back as a whole
sector (AFAIK). Other Flash chips have very large sectors that
need a separate SRAM to copy them into, and the erasure of
those large sectors when writing back can take some time (many
seconds), whereas small sectors can be modified in a few 10's
of ms

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