Here's something I just added to my web page.  It caused me enough grief
that I though I'd post it also, to make sure everyone using the SX sees
it.

Cheers,
Eric

The SX-Key allows you to configure the erase and program times.  The SX
was originally specified to use 10 ms/word program times.  However, the
20-Feb-1998 errata for the revision 2.1 parts states that 100 ms should
be used instead.

There is a temptation to find the smallest values that seem to work, and then
to back off somewhat.  For example, I've found that at a setting of 50 ms,
the SX-Key rarely reports errors.  (Note that it sometimes reports programming
errors even at the suggested 100 ms timing.)  However, you should exercise
extreme caution in your choice.  I found out the hard way that just because
the SX-Key doesn't report an error, doesn't mean that the part has programmed
properly.

Some code I was debugging was behaving very strangely, and I just couldn't
figure it out.  Finally I tried increasing the programming time back to
100 ms, and all the problems went away!

Apparently the SX-Key doesn't verify the flash memory in the SX at the normal
operating speed.  If the flash cells aren't programmed long enough, they will
read correctly with a long cycle time, but not at the full operating speed.