27 Jun
2005
27 Jun
'05
2:49 p.m.
Intel changed the specifications of the 2708 a couple
of times, later docs
state it does not require programming from address 0.
But did they also change the design of the chip, I wonder. Later 2708s
may be more forgiving as to the programming algorithm they'll accept.
Since Intel were so definite about having to go through all locations in
order n times in the data sheet I have, I would certainly want to do it
that way. Other methods might well damage the chip or lead to poor data
retention.
I have changed individual bits (only from a high to low, to go from low to
high the entire chip must be erased).
You can change individual bits, sure. The data sheet tells you how to do
that.
You have to go through _all_ the locations. If a locations is to be
unchanged, you program it again with its current contents (a special case
of this is that if you want to leave a location totally unprogrammed
after erasing the chip, you re-write it with 0xFF).
The later docs still state sequential writing but no longer require starting
at 0 but I have written non sequentially and can swear by that. I wrote a
program that verified before writing to speed up programming, this skipped
Oh, it probably worked. But I wouldn't recomend doing it. 2708s are
getting harder to find, so I'd not want to risk damaging one. And I
certainly don't want to have to trace a fault caused by an unreliable bit
in an EPROM. I would follow the manfacturer's instructions...
It reminds me af a friend who programmed 27128s with a single 1ms pulse
per location. It seemed to work. They verified OK. And then a bit later
on he got data-rot....
-tony