Reading PALs

Jim Brain brain at
Tue Feb 21 02:51:46 CST 2017

As a function of "give a man a fish, you feed him for a day; teach a man 
to fish, you feed him for all time", I dloaded Logic Friday, and figured 
out a quick way to read the two 16L8 (combinatorial only) PALs on the 
board with my EPROM reader (cue duct tape and baling wire snickers).

After getting some good reads, and minimizing the binaries (I read 8kB 
of data, and then split the files into 1kB chunks to handle the one 
unit's 10 input lines, and split the other file into 4 2048 byte chunks 
due to the 11 inputs), I then wrote a really crappy C program to convert 
the data to CSV format for Logic Friday.

After dealing with some nuances in the format, I was able to minimize 
the equations, and I thank you Chuck (I probably am still going to hit 
you up on the 16R4 and the 16R6, as I assume they are not so easy to 
reverse engineer) for the suggestion.

Now, my new question:

Is there a way to get Logic Friday to perform "negative" logic? 
Specifically, by looking at the CSV file, it is obvious that one of the 
outputs is low only when A15:A10 and R/W are all low.  So, basically:

O3 = (A15 + A14 + A13 + A12 + A11 + A10 + R/W)

But, what I get is:

O3 = A10  + A11  + A15 A13' A12'  + A14' A13' A12  + A14 R/W'  + A13 
R/W'  + R/W

I assume this is the "wetware" process you mention, but I thought I 
would check if I need to tweak something in Logic Friday to achieve 
better results.


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