newbie building a scratch-built computer

Tony Duell ard at p850ug1.demon.co.uk
Sat Aug 4 16:42:07 CDT 2007


> 
> Thanks for all the information everyone. I'm really looking into everything
> now, as far as building a computer from an off the shelf CPU such as a Z80
> or 6502. One thing that has occurred to me is that I will likely need an
> EPROM Burner. Where can I get such a device for a modern PC?

IMHO, more important than the EPROM programmer is an EPROM emulator. This 
is a box of RAM that connectes to the EPROM socket of the target system 
(the board you'be just made) and also to a host machine (PC,  parallel 
port, serial port, USB?). YOu can quickly download perogams into the 
emulator, which then appears exactly as the EPROM does ot the target, and 
the latter can therefroe run said programs.

The advantage over using EPROMs is that you can re-write the RAM as many 
times as you like (EPROMS have a limited number of program cycles) and 
rewrite it quickly. Unless your programming is a lot better than mine, 
you will go mad if you have to wait 20 minutes for an EPROM to be erased 
and reprogammed. each time you want to make a change!

There have bnen seceral desings for such devices in Elektor magazine over 
the years (and I guess elesewhere). The one I put together (using the 
Elektor PCB) was just a handful of TTL parts and a couple of 32K SRAMs. 
It links to a PC parallel port (which downloads bytes into the RAM).

-tony




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