I don't think this approach to programming 2708's is at all valid. I've been
rummaging in the basement lately and may be able to find one of the
"moldy-oldies" (literally, as they've been wet) that has a programming
algorithm description in it among my old databooks not yet tossed.
The procedure you describe is a post-2716 algorithm (intelligent) which was
not promoted, even for the 2716. The stock method for the 2716 was to elevate
VPP to 25 volts, write data and address to the device, assert PROG, wait 50
ms, negate PROG, and then proceed to the next byte. I used commercial
programming hardware and didn't give the 1702 or 2708 algorithms a moment's
thought, back then, but it has come up a few times.
Keep in mind that there are numerous DIFFERENT ways to do the job, and each
mfg has a preferred method that you should observe.
http://ee.wustl.edu/~info/docs/2708.pdf is a datasheet with progamming info
for the Motorola part.
Dick
----- Original Message -----
From: "Loboyko Steve" <sloboyko_at_yahoo.com>
To: <classiccmp_at_classiccmp.org>
Sent: Monday, May 06, 2002 9:21 AM
Subject: 2708 Programming Algorithm?
> 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
> 2. select address and data (start at addr 0)
> 3. bring PGM line from 0 to 27 volts for 1 mSec, then
> drop back to 0 (this seems very strange)
> 4. repeat 100 times per address (not all at once,
> increment the address lines and loop to avoid
> "overheating" a byte.
> 5. drop /OE and verify.
>
>
> Does anybody have an authoritative description, and a
> current requirement for the +5, +12, -5, and
> programming pulse? Thanks.
>
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Received on Mon May 06 2002 - 13:08:10 BST