From: Richard Atkinson (rga24_at_cantab.net)
Date: 2002-07-03 02:19:49
Marko Mäkelä wrote: > > There was some discussion on the cbm-hackers mailing list on reverse > engineering the programmable logic arrays found in Commodore computers. > Simple formulae can be obtained by guessing from truth table dumps and > verifying the guesses with a program that transforms the logic equations > to truth tables that can be compared to truth table dumps from real chips. > > Last night, I wrote the following two programs: > > http://www.funet.fi/pub/cbm/firmware/computers/c64/pla.c > http://www.funet.fi/pub/cbm/firmware/computers/plus4/pla.c > > These contain the logic equations for the C64 and plus/4 PLA, > respectively. Thanks to William Levak for providing me with the truth > table dumps. > > By the way, does anyone know what the output F0 of the plus/4 PLA could > have been used for? It is '0' whenever the inputs I15..I0 are 0111 011x > 1001 011x, and '1' otherwise. In other words, the signal is low > whenever the address is $fd2x and RAS is low and PHI0 is high. It accesses the custom chip in the V364. I think it has four registers. Richard Message was sent through the cbm-hackers mailing list
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