Stephen Shaw <bottrawler@junkbuster.zzn.com> wrote:

> On Sun, 15 Dec 2002 16:13:45 +1300, David Empson wrote:
> 
> > Herbert Fung <lemonherb1@netscape.net> wrote:
> > 
> >> Hi, I was wondering if there is any specific type of EPROM one would
> >> have to get to burn repacements for various Apple II related cards.
> > 
> > It depends on the card.  Older cards (or simpler ones) might use EPROMs as
> > small as the 24-pin 2708 (1KB).  The 24-pin 2716 (2KB) and 2732/2532 (4KB)
> > were also commonly used on older cards.
> 
> 2708s are obsolete and most EPROM programmers that can handle the 2716s
> upwards do not seem to handle the 2708 (different programming voltage?).

Yes, the 2708 was pretty horrible - it needs both positive and negative
voltages for burning.  The 2716 was the first EPROM able to be burned
with positive voltages only (usually +25V).

Later EPROMs reduced the voltage required.  Current ones (27C512 and
larger) use about 13.5V for the programming voltage, but they also raise
the Vcc input to 6V during programming.

Modern Flash ROMs can be programmed in-circuit with only a +5V supply.

-- 
David Empson
dempson@actrix.gen.nz