From: Marko Mäkelä (marko.makela_at_hut.fi)
Date: 2002-06-24 13:58:22
Gideon Zweijtzer wrote: > Yes we are talking about the same thing. I am just trying to hint to a way > to obtain elegant equations from a truth table. If you would read out the > PLD like an EPROM, just the way you and others did it (Side note: I didn't read any PLAs as an EPROM; I've only analysed the resulting binary images.) > case inputvector is > when "000" => outputvector <= '0'; > when "001" => outputvector <= '0'; > when "010" => outputvector <= '1'; > -- ... etc > end case; Okay, that's just a different way of putting it. But I would expect a VHDL tool to crash if it was fed 2^20=1048576 lines like that. Want to give it a try? I haven't done any VHDL stuff, and I don't have easy access to any commercial software, including Microsoft Windows. Converting the binary data to your proposed format or to CNF or DNF is straightforward with a few lines of Perl or C. > If you want to improve readability, you can replace the words inputvector > and outputvector to a set of signal names that are actually used on the > Commodore board. Yes, but labeling doesn't eliminate "don't care" variables or reduce the number of terms in a CNF or DNF equation, which is (in my opinion) the main reason of unreadability. In the worst case, each output can be a function of all 20 inputs (I'm assuming that the C128 PLA has 20 inputs). Marko Message was sent through the cbm-hackers mailing list
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