Re: Burning EPROMs

[david@uow.edu.au (David Wilson)]

"Stephen Shaw" <bottrawler@junkbuster.zzn.com> writes:

>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?).
>I have a lot of Epson APL printer cards minus their 2708s :(

It is worse than the programming voltage - it needs three voltages just to
work in read mode! Watch out for TMS2716 parts as they are 3 voltage as well.
TI made TMS2516 parts to match the Intel 2716 with single supply.

            2708
    +--------\/--------+
 1 -|a7             vcc|- 24	vcc = +5v
 2 -|a6              a8|- 23
 3 -|a5              a9|- 22
 4 -|a4             vbb|- 21	vbb = -5v
 5 -|a3           we/cs|- 20
 6 -|a2     2708    vdd|- 19	vdd = +12v
 7 -|a1         program|- 18	vpp = +25v
 8 -|a0              o7|- 17
 9 -|o0              o6|- 16
10 -|o1              o5|- 15
11 -|o2              o4|- 14
12 -|gnd             o3|- 13
    +------------------+

Here is a useful diagram of all 24 and 28 pin 27xxx series EPROMs.

http://www.geocities.com/SiliconValley/Peaks/3938/gfx/eprom.gif
--
David Wilson  School of IT & CS, Uni of Wollongong, Australia