2708 Programming Algorithm? - test-drb@ccmp.vtda.org

6 May 2002

...
 From: ajp166 &lt;ajp166(a)bellatlantic.net&gt;

 >> I just remember that all the 87xx parts,
8741, 8755, 8748/49, etc, were all
 >> 5-volt parts.  further, I'm not at
all sure that the 8080 had below-ground
 >> signal levels, since they were intended
to be attached to bipolar parts, e.g.
 >> 8212, etc, which would have been
intolerant of that.  What I've got in my lap
 >> is the 8080A data, which may, actually be
different, but IIRC, the 8080 needed
 >> the negative bias supply so it could
swing to ground and the +12 so it could
 >> swing to a reasonable high level.  My
only contact with the 8080 was on boards
 >> made by Intel, and, while I poked around
with a 'scope and other gear from
 >> time to time, I don't recall ever
finding an address, data, or control signal
 >> that wasn't TTL compatible. 

Wrong! the 8080 and 8080A had basically the same levels and drive.  the
issue
of negitive voltages on the output is a red herring. 
 I guess I'm wrong here. I just remember something about negative swings
but it was a long time ago.

...

The 8708 accoring to the 1978 8048 manual is a THREE voltage part with
the exact pinout  as 2708.  It's of course an intel number to allow the
"kitting:
practice that intel did do back then... "FAE>>> ya gotta use 8xxx
parts". 
 They did make changes in some cases with the leading number.
The 4702A was different than the 1702A in that the negative
rail could be -10V instead of -9V, although, the 4702A would
program and function at -9V. Maybe this is what was confusing
me.

...

Now for a note,  looking at the 1979 Intel component data book the 2708
is
listed and save for a faster programming method the 8708 is identical per
notation in the data book!

Recommended programming pusle width is .1 to 1 millisecond and the
programming loop should not program any location for more than a total
of 100mS.  Though I remember programmin them using a 1ms pulse and
doing a read to see if it took, programming it 5 times more for over
program and looping till it took and moving on to next location.  If a
location
took more than 90 hits is was flagged as bad.    That seemed to get the
best life out of the parts according to my notes.  FYI: over eraseing
them seemed to kill them too. 
 These can be baked if they are in the ceramic package. This
brings them back to life. When I was in the lab, we did this
often. I don't recall the temeperature we used.
 The 2716's were more robust. We left some under the UV light
for weeks and had no data retention problems ( although, we
only required them to hold for about 6 months instead of 10 years ).
Dwight

...

Programming voltage is nominal 26V pulsed!  All other votages are static
(Vcc, Vdd and Vss) with  *ce/we being driven as needed for read or write.

    That's not the point. The point is that the
inputs and outputs are TTL (0V/5V) level and not a negative voltage.  FWIW IIRC even
the 8008
had a fan out of more than one. I have the manual and can look if it
matters.

Correct it was 2 LS loads.  And the old 4004 was ttl if used with the
correct supply
voltages -10 and +5 wich was typical of the PMOS logic.

Allison