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From: rainer@boulder.Colorado.EDU (Rainer Malzbender)
Subject: Re: Design of vending machine.
Message-ID: <1991Mar23.074949.19060@colorado.edu>
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References: <2460@umriscc.isc.umr.edu> <1991Mar22.192022.3538@colorado.edu> <2463@umriscc.isc.umr.edu>
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Date: Sat, 23 Mar 1991 07:49:49 GMT

In article <2463@umriscc.isc.umr.edu> robf@mcs213j.cs.umr.edu (Rob Fugina) writes:
>
>My point is that the point of the assignment is probably to make it with
>state machines and combinational logic.  If that's what a PAL is, then I
>submit...but *I* don't know anything about PALs (please tell me where I
>could learn) and my opinion is that it would be easier for this person to
>just use the 7 different ICs...  so where do I get info on PALs???

Well, I just tried mailing a long-winded explanation of PALs, but it bounced.
Picture a bunch of and gates, or gates, and flip flops in a bag, and wire
them up any way you want to. That's a rough idea of what something like
a 16R8 registered PAL is, and that's the very bottom of the food chain as
far as PLDs (programmable logic devices) go. By all means, check out the
second edition of "The Art of Electronics" by Horowitz and Hill, an issue
of Byte on programmable hardware a few years ba, and maybe an AMD/MMI
data book ("Pal Device Data Book"). If you've never used them, you'll
be pleasantly surprised; I was. The best deal is you can write a high
level program to burn these babies. A single 20-pin chip can act as a state
machine with 256 states (although chances are you won't be able to decode
all of them with only the on-chip logic).
--
Rainer Malzbender, PhD  "It's not the bullet that kills you, it's the hole."
Dept. of Physics (303)492-6829                             -Laurie Anderson
U. of Colorado, Boulder         rainer@boulder.colorado.edu 128.138.240.246