10 Sep
2015
10 Sep
'15
11:19 a.m.
From: ard at p850ug1.demon.co.uk
To: cctalk at classiccmp.org
Subject: RE: 21MX proms (per request
Date: Thu, 10 Sep 2015 14:14:44 +0000
Your right, I didn't say that the 2716 was not a single rail, just that it
didn't have a separate Vpp and PGM pin. It was programmed by turning
Vpp on and off. I could be wrong that the 2732s were that way as well.
The TI 2716s were not so friendly.
Intel sold half bad 2716s for 5 volt 2508s. Even after 2716s price dropped,
they still sold 2708s for $32 when you could buy a 2716 for $3 to $4.
Dwight
2716 are that last of the program by turning the
programming voltage
on and off.
I must be mis-remembering how I designed my first EPROM programmer. I
know I could do 2716s (single-rail, not the TI ones) and I thought I always
applied Vpp and pulsed another pin at TTL levels to program them
IIRC the 27128 was the last one to actually allow the 'dumb' 50ms
programming algorithm. It may well work on larger chips, but
I never tried it. That's why I designed my programmer to do
2716s, 2732s, 2764s and 27128s only. Not having another
programmer I couldn't use a microprocessor or microcontroller
(no way to load the firmware) so I had to do it all in TTL logic.
Doing the 'intellegent' algorithm in TTL was a bit much ;-)
-tony