Reading PALs

[Alan Hightower]

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