So basically you make a truth table by "trying" all the possible input combinations and see what's on the outputs and store that, right ?
Hmmm, no that's actually more like the way you dump protected GALs/PALs.
What I do, is just consider the PROM dump as one big truth tabel, with the address lines as inputs.
Then I look at the data one column at the time and every time I meet a 1, I look at the address bits and spit out the corresponding product-term; there's actually not anymore to it. I don't do any fancy stuff like reduction or anything.
Very cool solution ! 
Thnx! ...and thnx you other guys, as well };-P
Do I understand you wrote your own software for your Eprom programmer?
Yup, but I only implemented the stuff that TopWin6 (the stock software for Top2005+) lacks IMO.
Would love to have a Windows (OSX preferred, but I must stay realistic 
) program that could support the Needham EM-10. But I guess it's more a hardware issue....it uses the parallel port and most more modern hardware simply is too fast or doesn't support the native mode good enough.
Yeah, that sux. I don't think it's possible. But if the programmer doesn't use very precise timing through the parallelport, you might be able to use one of them USB-thinggies. I know the Fluke9010a is able to use them
http://elgensrepairs.blogspot.dk/2012/12/retrofitting-usb-port-on-fluke9010a.html ... have you ever tried one of those?
EDIT: Argh shoot! I now see, that the Fluke uses the serial port and not parallel, sorry...
