Hello,
After building several Apple 1 and Apple II replicas, I had the crazy idea of building a Lisa replica from scratch.
Gerber PCBs are available, board production is not cheap, but you only live once :) I have all the parts needed for the build, except for the COP421.
Precisely. I have new (10pcs) COP421 DIP28, but I don't know how to program them? Does anyone have any ideas on how to program these chips? The BIN is available.
An alternative is to use this COP402/404 to COP421 adapter ( http://john.ccac.rwth-aachen.de:8000/patrick/COPSreader.htm ), but ironically - I can't get a COP402/404 anywhere.
HELP:)
Mateusz SQ9PXB
You cannot program a COP421 microcontroller. It seems to have a mask ROM, which means it can only be programmed during fabrication.
If you have the BIN file, you need to use an "emulator" like this one, which is basically a COP400 family microcontroller that works with an external PROM chip. You can find the COP402MCPN chip on eBay: https://www.ebay.com/itm/225424422717
ee495fb328a5801e.jpg
Hi,
Thanks for your reply. Studying the factory documentation, I'm not sure what it looked like in the 1980s. The most interesting thing is that my local vendor has new COP421L-JRL-N chips. But so what? It has to be programmable somehow....
Buying a COP402 from eBay from the US is a problem – very high shipping and customs costs per unit.
In my opinion, the optimal solution would be to replace the COPxxx with a modern PIC/AVR-style uC. You'd need to know exactly what commands the original COP421 transmitted to remap it.
Regards,Mateusz SQ9PXB
In the early 80s to program a COP400 family microcontroller you would get a COP400 Product Development System. It contained a ROM-less COP chip and some PROM sockets. You would use it to write and debug your code and when you are done you would send the ROM to National. They would produce for you thousands of COP chips with masked ROM containing your code. Some of these preprogrammed chips will be left unused, survive until the present day and be sold as NOS to unsuspecting customers.
COPSDevSystem.png
Source: https://seanriddle.com/NSC_COP400PDS_Users_Manual.pdf
What caught me off guard was that the store had a large number of COP421s. So I wonder what's in their ROMs :)
Unfortunately, it turns out that getting a COP402 for the adapter will be my biggest challenge with this project...
I hope so.
Regards,
Mateusz SQ9PXB
Here is another listing from China. Higher price than the one from the US, but the shipping to Poland is very cheap. Looks like it's the same seller with two different accounts. He accepts offers, so you can ask him to match the price of the other listing: https://www.ebay.com/itm/315553382173
Yes, I saw that Chinese ad, but it seemed suspicious to me. There are identical photos in another ad from a US store. I'm worried the Chinese seller might be a scammer.
BUT
I just bought the Soviet equivalent of the COP402 -KR1820VE1A, from a Lithuanian store for only 1.50 euros. Unfortunately, only one pcs was available. I hope this works.
https://www.evita.lt/en/m-1820ve1a-kr-microcircuit-kr1820ve1a?search=KR1820VE1A
Regards,
Mateusz SQ9PXB
Very nice! I love using Soviet and other Eastern bloc alternatives myself. They are super cheap, available in huge quantities and no one fakes them. With Soviet ones just be sure to use slotted sockets instead of machined ones, because they are metric and do not align perfectly.