Re: Strange EPROM Adapter Found

["Roger Johnstone" <bhmhome@es.co.nz>]

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In article <230919992031335129%news001@macgeek.org>, Bryan Villados
<news001@macgeek.org> wrote:


>Hi, guys!
>
>Digging in my old computer junk, I came across something I'm curious
>about... My dad (he passed away a while back) used to tinker with
>EPROMs, and he used to burn them all the time. I found an adapter he
>made... It's a 24-pin adapter (Textool) and he left in it a 2716 EPROM.
>I believe he made it so that he could stick this adapter into an
>existing ROM port (on an Apple II logic board, card, etc.) then pop an
>EPROM into it.
>
>Here's the thing I'm curious about... On the adapter he jumpered pins
>21 and 24, and pins 18 and 20. What's the purpose of doing this????
>
>---
>Bryan Villados
>Curator, Apple Museum For-a-Day, Hawaii
>http://www.macgeek.org/

EPROMs and mask programmed (mass produced) ROMs have slightly different pin
connections and so you need an adaptor to use an EPROM in place of a mask
ROM.

On a 2716 EPROM pin 18 is chip enable/program, pin 20 is output enable. Both
of these should be tied low to read from the chip.

Pin 21 is the programming supply, 25V is applied during programming. Pin 24
is the normal supply. Both of these should have +5V on them.

Roger Johnstone