21MX proms (per request

[tony duell]

> 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