Thanks for mentioning Logic Friday. I had never heard of it. I just used it to great effect in an unrelaed combinatorial logic reduction problem!
-Alan On 2017-02-18 20:37, Chuck Guzis wrote: > On 02/18/2017 04:22 PM, Jim Brain wrote: > >> Seems like someone on list was willing and able to read PAL16L8s and >> give a try to some PAL16R4s... Is that person still on list and >> still interested? If so, please contact me off-list. >> >> I am trying to restore some C64 carts, and the PAL on my working unit >> is protected, so I cannot replicate. > > If I'm the person (see my blog on vcfed.org), "reading" isn't exactly > the right term. For purely combinatorial PALs, the technique is to > determine the input and output assignments, then exhaustively run > through all the combinations. Take that data and run it through a logic > minimizer, such as Logic Friday and then use a bit of wetware to pick > out tristate control lines and their corresponding outputs. > > Not foolproof by any means--and much less so, if the device is > registered, but very often successful. > > A schematic showing the part application can be a godsend. > > --Chuck