[Coco] 128K/256K EEPROM Cartridge board

[Chad H]

I had to make separate 'models', one for the PDIP and another for the PLCC as there was insufficient room on the board without making it larger.  The 32-pin PDIP  BARELY FITS!  For those that are interested I just put up animations of the prototype designs on YouTub..

32-pin PDIP >> http://tinyurl.com/lhpy9xt

32-pin PLCC >> http://tinyurl.com/m3b7b3d

I added a jumper for "Write Enable" that connects the WE# pin to the Cart R/W pin when jumpered, else it pulls high by pullup resistor (10K I'm figuring).  This of course will be to experiment if we can flash the chips from the CoCo.  If anyone sees a issue here please advise me before I order the first batch!  Thanks!

- Chad

-----Original Message-----
From: Coco [mailto:coco-bounces at maltedmedia.com] On Behalf Of Chad H
Sent: Sunday, January 25, 2015 10:28 AM
To: CoCoList for Color Computer Enthusiasts
Subject: [Coco] 128K EEPROM Cartridge board

I was browsing prices on the 2764, 27128, 27256 and 27512 EPROMs this morning noticing how they are slowly getting more scarce, especially the 27128.  Also, the prices are not the best.  Ironically, at least to me, the 27512's with most capacity are the cheapest.  

Then I remembered I had a box of like 20 or so 29EE010 EEPROMs that I had ordered a few years ago. I only needed one to upgrade my Win'98 machines bios chip but was cheaper to buy the lot.  In any case, these are 128k parallel EEPROMs 150ns in the DIP 32-pin package and go for about $1.70 easy.  Even better, I can get the PLCC version for $0.25.  I know my old Willem programmer works with them and I wouldn't have to wait on UV erase cycles.

I have the idea of revamping the 2764-27512 EPROM boards I've been building, removing the existing DIP layouts and adding the option to mount either the DIP or PLCC version of the 29EE010.  I would also need to add one additional jumper for the A16 address line.  This would give more capacity for roms , each selectable by jumpers...

16 x 8K
8 x 16K
4 x 32K

I'm going to go ahead and work up some prototypes on this.  I'm wondering how much interest would there be out there in this?

- Chad

Sent from my Transformer Infinity

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