[sdiy] Protected PAL/GAL reading service?

Rainer Buchty rainer at buchty.net
Mon Feb 18 13:33:59 CET 2013

On Mon, 18 Feb 2013, Magnus Danielson wrote:

> Does not always help. If internal feedback is being used, then it 
> becomes a bit more tricky. In the PPG Wave 2.3 PALs, the feedback 
> available on chip was not used, so it was wired on the board for one 
> of the PALs. Ah well.

Right you are.

But for creating the truth table (and also creating the equations), that 
shouldn't matter. You step through the input bits and measure the output 
bits after $t ns of settling time. After all, the output pattern will 
directly depend on the input pattern as everything is combinatorial. All 
you get is visible intermediate products (the feedback sits after the 
tristate buffer).

For 16R8/V8, things look differently, of course. But for L/H, feedback 
should not impose any problem.


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