EPROM
ERASER
INTRODUCTION
The idea
to make an Eprom eraser (Erasable Programmable Read Only Memory) come
after building an eprom programmer (that you'll find on my web); those Eprom,
infact, are different from EEprom (Elettrically Erasable
Programmable Read Only Memory) because it need UV-ray to be erased;
I've worked with 27C32,27C64,27C128, 27C256, 27C512 but what you'll read
here is true for all the eprom of that family.
Before
programming an Eprom it must be erased (all bit must be "1" -
"FF" in Hexadecimal code); infact it is possible only write "0";
as I said, to erase an eprom you need a UV-C ray "C" with a wave
lenght of 253,7 nanometer;
pratically we can use a common germicidal neon,
not difficult to find.
On the
datasheet you'll find the exact instruction to erase an eprom, but generally you
need about 15-20 minutes at about 2,5 cm from the UV light (for radiation of 15
W-sec/cm*cm);
you can reduce the time putting the eprom closed to the light;
After same erasing you'll find your exact time.
Avoid to take the eprom under the UV ray for long time, that can damage the
eprom and remember that erasing after easing, the eprom will slow down the
access time (but this is not really a big problem);
Before erasing be shure the "erasing window" is clear, if not use
alcool to clear it.
73 de iz7ath, Talino