I do believe you've misread part of the spec's, Joe. The 8708, IIRC, is a
5-volt-only version of the 2708, otherwise masqueraded as the 2758. I got one
of these back in the mid-late '70's, on an 8748 evaluation board, and as such,
it was my first 5-volt-only EPROM. They were described by the Intel FAE as
2716's with a flaw in one half or the other, and they were available in two
types, with either a high or low enable where the 2716 had an address line.
Dick
----- Original Message -----
From: "Joe" <rigdonj_at_cfl.rr.com>
To: <classiccmp_at_classiccmp.org>
Sent: Monday, May 06, 2002 3:29 PM
Subject: Re: 2708 Programming Algorithm?
> Steve,
>
> I don't have the programming instructions for the 2708 but I do have them
for the intel 8708 and intels later manuals state that they're the same.
Here's what I have in the sept 1975 8080 Microcomputer Systems User's manual.
>
> At 08:21 AM 5/6/02 -0700, you wrote:
> >I obtained a bunch of 2708 UVEPROM's, and I'd like to
> >be able to program them. As you may know, they require
> >a different algorithm than the 2716 and on, and three
> >voltages, +5, +12, and -5.
> >
> >I'm building a little board that will program 1/2 (the
> >upper or lower) of a 2716 to a 2708 (I can program
> >2716's). But I can't find a description of the
> >algorithm that is detailed enough. What I think I know
> >is:
> >
> >1. The /OE line must be high
>
> Intel says to raise the CS*/WE line to +12 volt.
>
>
> >2. select address and data (start at addr 0)
>
> Correct. A note here says that the logicx levels for the address, data
and voltage supply lines are the same as for the read mode.
>
> >3. bring PGM line from 0 to 27 volts for 1 mSec,
>
> Correct except you can use 25 (min) to 27 (max) volts according to the
manual.
>
> then
> >drop back to 0 (this seems very strange)
>
> You have to allow for the setup time for the new address and data. The
times are 10uS (min) for each but they could be different for the 2708.
>
> >4. repeat 100 times per address (not all at once,
>
> NO. This isn't what's in the intel manual. It says one programming pulse
per address per loop. And that a loop is one pass through all the addresses.
You have to repeat the loop until N (passes) x Tpw (programming pulse width)
>= 100mS.
>
>
>
>
> >increment the address lines and loop to avoid
> >"overheating" a byte.
> >5. drop /OE and verify.
>
>
> "Note that programming and read loops can be alternated"
>
>
> >
> >
> >Does anybody have an authoritative description, and a
> >current requirement for the +5, +12, -5, and
> >programming pulse? Thanks.
>
> It varies according to the temperature but the max occurs at low temp and
is about 11ma for Icc _at_5.25v, 65ma for Idd @12.6v with CS*/WE high and about
35 ma with CS*/WE low, 41ma for Ibb _at_-5.25v with CS*/WE high and about 17ma
with CS*/WE low.
>
> The programming pulse current is typically 10mA with 20mA max.
>
> Have fun!
>
> Joe
>
>
> >
> >__________________________________________________
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> >
>
>
Received on Mon May 06 2002 - 13:51:21 BST