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]

I saw someone post something like this on the old site. They used a 27c256 or 27c512.

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.

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.   

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!

[jay]

Now the hard part..... getting the data off the old bi-polar proms.....

[Stolistic]

Pretty sure you could swap the sockets and put the thin CAP socket on top, and wide eprom pins on the bottom and read it in with a standard burner as a 27c512 and truncate off the excess data.  The mapping of the pinout would remain the same, just the placement of the sockets would change.

[jay]

That makes some sense but I thought there were dual voltages required to operate the older chips. Other wise why would my burner not simply support the chip via an adapter like they do others.

[Stolistic]

That makes some sense but I thought there were dual voltages required to operate the older chips. Other wise why would my burner not simply support the chip via an adapter like they do others.

The dual voltages generally refer to the fact that burning the chip requires a different voltage than reading it.  Reading takes much less voltage, so if you just want to read the chip, you should be fine.  I put my CAP in a breadboard and read it fine with a 5V regulator tied to the pins to light up some LEDs.  I'll probably build an equivalent adapter and try it out sometime in the near future.

[Stolistic]

I built a crude example this afternoon to test my theory. 

Its ugly but it works.  After you read the CAP in, you need to trim everything starting at 0x200 to the end of the file, so all you have is 0x000 through 0x1ff.

If you are reading in a normal CAP you have to interlace a row of 32 0xFF's every other row starting at 0x020 and ending on row 0x1e0.  I didn't read in a superboard prom (CAPX) but assume you would leave the data as is, making sure rows 0x100 to the end of file is all 0xFFs or all 0x00s.

Pictures are below:

[2Nutz]

I built a crude example this afternoon to test my theory. 

Its ugly but it works.  After you read the CAP in, you need to trim everything starting at 0x200 to the end of the file, so all you have is 0x000 through 0x1ff.

If you are reading in a normal CAP you have to interlace a row of 32 0xFF's every other row starting at 0x020 and ending on row 0x1e0.  I didn't read in a superboard prom (CAPX) but assume you would leave the data as is, making sure rows 0x100 to the end of file is all 0xFFs or all 0x00s.

Sweet, I like the adapter to read the PROM's.  Looks like I need to make a run to RatShack and/or HSC this weekend.

Confused on the rest of it though.  On a regular CAP, after reading it with the adapter you install 2 rows of 0x00 to extend the data to restart at 0x40 for 2 rows and then 2 rows of 0x00 at 0x60, 2 rows of date at 0x80, etc ?  This is necc. to make it read correctly once burnt onto a 27c512?

000: DA TA DA TA DA TA DA TA DA TA DA TA DA TA DA TA
010: DA TA DA TA DA TA DA TA DA TA DA TA DA TA DA TA
020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
040: DA TA DA TA DA TA DA TA DA TA DA TA DA TA DA TA
050: DA TA DA TA DA TA DA TA DA TA DA TA DA TA DA TA
060: 00 00 00 .............................. . . ... . ..

Also, this process is not necc. for a CAPX and the data ends at 0x0ff ??

Just trying to get my few remaining brain cells around this.
       

[Stolistic]

Yes, you got the concept.

CAP Data after reading it in:
0000: 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
0020: 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02
0040: 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03
0060: 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04
...etc...

CAP Data after editing:
0000: 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
0020: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
0040: 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02
0060: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
0080: 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03
00A0: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
00C0: 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04
00E0: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
...etc...

I have not read in a CAPX (superboard) yet, so cannot confirm, but from what I've seen, it appears you just leave the data alone.

Have fun soldering and be sure to test all your connections for breaks and continuity before you use it.  Post a pic if you get it working.

[Stolistic]

** UPDATE **

I tested the adapter with a CapX chip and with a normal Cap and things work just great.  However, my initial discussion about the non-CapX chips needing the data interlaced with FFs is INCORRECT.  The data read in is in the proper order.  So the reader works the same for both CAP and CAPX chips.  No need to make edits afterwards.

-------------------------------------
On that note:

I'm going to be sending the design off for PCB manufacturing, and would like to get a count of people interested in purchasing a board or two.  Depending on the results, the price will be lower.  But an initial estimate puts them in the range of $10-$12 each for a small quantity.

So if interested, either plop a reply here or send a pm.  Be sure to note what type of adapter you would like and quantity.  Remember the pcb design allows for either a cap reader or a cap replacement.

Example request:
Qty 1 - CAP Reader Adapter
Qty 3 - EPROM to CAP Adapter

I'd like to order before month-end so please reply if you think you may be interested.  Just trying to get a ballpark idea of the batch size.

Thanks!

[jay]

Please sign me up for 1 Cap to Eprom adapter.

[2Nutz]

Sign me up for:

Reader = Qty. 1
Adapter = Qty. 2

Saves me the time of rounding up parts and assembly.   

FWIW, Jameco current catalog shows single unit M27c512-45xF1 at $2.65, 10+ at 2.39 and 100+ at 2.12 each.

[Stolistic]

Just to clarify, it will include all the sockets and be assembled and tested, but you will need to purchase your own EPROMS.

[PowderMaker]

I'm in for:

Reader = Qty. 1
Adapter = Qty. 2

Thanks!

[knagl]

Please put me down for 2 EPROM to CAP adapters.

[Stolistic]

Small bump to see if anyone else is interested in ordering some reader or adapter boards.  I'll probably work on placing an order by end of the week and let everyone know when they are available.  I'll be adding extra quantities onto the order in case someone inquires later.

Thanks!

[CommTech]

I'm in for One of each (Reader and Adapter) also.

Thanks!

[Rep]

Sorry for the delay, I'm in for one of each also! Cool stuff!

[PowderMaker]

What ever became of this project? Did these boards ever get produced?

Thanks,

[brichter]

I'm in for one of each. 
2nutz, you can go to HSC, just stay away from my retail stash of Molex connectors.

[Forrhouse]

If it's not too late, I'm in for:

Qty 2 - EPROM to CAP Adapter

Thanks,
Eric

[jay]

I am still in for 2.