This stuff's already been corrected, and the only thing with which I'd take
issue is your assertion that it's WRONG, since I said precisely the same thing
you said. It's been a long time since I looked at an 8708 or its spec's, and
I was just remembering what I thought I recalled from a trigger instantiated
by seeing the "it's a 5-volt world" slogan on that brocheure. It's been
firmly established, though not by me, but I believe it, that the 8708 is just
another 2708.
Dick
----- Original Message -----
From: "ajp166" <ajp166_at_bellatlantic.net>
To: <classiccmp_at_classiccmp.org>
Sent: Monday, May 06, 2002 6:00 PM
Subject: Re: 2708 Programming Algorithm?
> >>> 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.
>
That was, exactly, my point, Allison.
>
> 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".
>
Maybe so, but I didn't listen. By the time it mattered, the 5-volt parts were
readily available.
>
> 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.
>
> 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
>
>
Received on Mon May 06 2002 - 19:52:29 BST