Rochester, 31 augustus 2005.
 Dear all,
 Yesterday I received my $12.50 JDM programmer from eBay and now I can=20
finally program the 16F628A (for some reason the El Cheapo can handle the=
=20
16F628, but not the 16F628A, regardless of software used). So I happily=20
reassembled my application for the new target, programmed the device and=20
used it. At first all seemed to be working fine, but then I started noticin=
g=20
little glitches.
 I was already aware of some differences (the 16F628A consumes less power=
=20
and uses a different programming method) and I had read in the datasheet=20
that the configuration bits changed, that code protection is no longer=20
partial, that timer 1 and the internal oscillator work differently but this=
=20
was something else.=20
 I debugged for a while, and then I discovered that the 16F628A doesn't=20
allow you to read the EEPROM while it is writing to it. On the 16F628, if=
=20
you read the EEPROM while writing to it, it returns 0xFF and writes the=20
correct value. On the 16F628A, if you read the EEPROM while writing to it,=
=20
it returns 0xFF but also stores 0xFF into it, instead of the requested=20
value. This is a rather unfortunate difference, which is why I decided to=
=20
let you know.
 Of course, I tested this only with two 16F628 and two 16F628A that I bough=
t=20
at the same time. It might be that some 16F628 exhibit the same behaviour=
=20
and that some 16F628A don't. But it really seems like something that has=20
been introduced in the 16F628A.
 Greetings,
Maarten Hofman.
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