Adapter to Replace Color CAP PROM with EPROM
knagl:
Originally posted by Stolistic on 7/13/2008:
I got to thinking the other day about how hard it is to find replacements for the color PROM on the PE+ and decided to mock up a little adapter using a UV EPROM instead. The advantage would be being able to program them in a basic model programmer, since color PROMs generally require special adapters and high voltages.
One of the challenges with this project is that color PROMs have an access time near 60ns, and most EPROMs today are 250ns or higher. After a bit of searching I found some fairly cheap EEPROMs on JAMECO that have an access time of 45ns. They are M27C512-45XF1 and run about $2.35 each. They are a bit overkill in memory size, but the price is right.
So I ordered a few and some 28-pin and 20-pin sockets to go with them.
All that was required next was to map the pins from the EPROM to the color PROM, and solder it together on a piece of perfboard. The 28-pin socket goes on the top, and the 20-pin socket goes on the bottom (with wires soldered through the board to connect to the bottom layer).
Below are some pictures of the final adapter installed and working in my PE+ machine. (Pictures pending at this time.)
I drafted a PCB layout and may consider making a bunch sometime, but for now my prototype is enough.
jay:
I saw someone post something like this on the old site. They used a 27c256 or 27c512.
Given the small size of the prom theoretically you could dump a number of these into a 27c512 and make it dipswitch selectable.
knagl:
Quote from: jay on December 29, 2008, 07:21:19 PM
I saw someone post something like this on the old site. They used a 27c256 or 27c512.
Quote from: knagl on December 29, 2008, 07:09:31 PM
Originally posted by Stolistic on 7/13/2008:
I gave credit - I was re-posting this for the sake of preserving the information, not to steal someone else's work. :) I'm actually in communication with Stolistic right now to try and get the pictures he posted.
Quote from: jay on December 29, 2008, 07:21:19 PM
Given the small size of the prom theoretically you could dump a number of these into a 27c512 and make it dipswitch selectable.
In fact, you posted that on the old thread. :71-
Quote
If you were to put in a bank of dipswitches - given the size you should be able to use 1 27c512 to do a whole series of Cap-Proms that you simply select.
You just select which memory space you use. Given the 1.85 cost of the 27c512s. I am not sure why you would want to complicate it though.
Stolistic:
Can't find my old pics, but made a new picture of the most important part below:
I'll snap a photo of the completed adapter sometime and update this page.
knagl:
Nice! Thanks for posting, Stolistic!
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