Re: PLA equations
Date: 2003-06-10 06:41:32

In reply to Ethan Dicks:

> > Since some of the early C64's used the 82s100 instead of the MOS 
> > 906114 can't this  GAL/adapter fix work on most c64 boards (rev A-C)? 
> {SNIP}
> As to the specific question, I can't comment on a GAL adapter, but
> in general, PLAs are more like ROMs than GALs... they are different
> internally and solve different design problems.  It may be possible
> to convert a specific PLA map to a set of GAL equations, but only
> on a case-by-case basis.  There's no general solution.

Actually, a GAL is a superset of a PLA, because a GAL contains a "PLA area" 
and configurable output cells with flipflops, while a regular PLA does not 
have the flipflops. When the flipflops in a GAL are not used, you actually 
have a regular PLA. IN other words, if your GAL has the same number of inputs, 
outputs and or-terms per line, you can always map a PLA to a GAL. IMHO there 
is no such thing as "GAL"-equations and "PLA"-equations. Both are just logic 

Now, to come back to the 82S100 problem: it has 16 inputs and 8 outputs. This 
is probably the biggest problem. I think that these large GALs are not very 
common. But they do exist! Take a look at the GAL26V12 from Lattice... an 28-
pin DIP package that even looks much like the 82S100. Different pinning 
though. the GAL6001 would maybe even better, since it has its power pins on 
the edges @ a 24-pin DIP pacakge. I can't remember though whether the 82S100 
is 24 pins or 28 pins.


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