Universal logic modules vs NAND-like modules

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Hi everyone,

Is there a proper name to distinguish NAND-like universal modules from
ordinary ones, that is, the ones formed by a function F, plus NOT, plus ONE,
and ZERO?

Thanks,
Candida
---
Candida Ferreira, Ph.D.
Chief Scientist, Gepsoft
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Re: Universal logic modules vs NAND-like modules
Question doesn't make sense to me.

Try again or pick up a logic book.

Maybe you refer to fixed logic v tablelogic?

So what brings someone in your esteemed field down into the hw
trenches.

johnjakson at usa dot com


Re: Universal logic modules vs NAND-like modules
NAND and NOR functions by themselves can be used to describe any other
function, including NOT, ZERO and ONE. But, for instance, the 3-multiplexer,
which is also by definition an ULM, can not by itself describe a NAND gate
as it is unable to create a NOT gate. But there are other functions that
behave exactly like NAND or NOR gates in the sense that, by themselves, they
can also describe any other function. Do such functions have a name? I think
there is something special about them and I would like to distinguish them
from the ordinary ULMs.

Candida
---
Candida Ferreira, Ph.D.
Chief Scientist, Gepsoft
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Re: Universal logic modules vs NAND-like modules
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other
3-multiplexer,
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gate
that
themselves, they
I think
them


I don't follow.  Multiplexers are as complete as any logic element.
I'm not sure what you mean by a 3-multiplexer, but I will assume you
mean a 2 input mux with a single control input.  You can get a NOT
function by putting a 1 on the I0 input and a 0 on the I1 input and
your signal on the sel input.


Re: Universal logic modules vs NAND-like modules

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That's true and does not contradict the definition of a ULM, but you need
the 1 and the 0 to create a NOT. Without them you cannot create a NOT with
the 3-multiplexer. But there are other functions, such as the NAND and the
NOR functions that, by themselves, can create any other function, without
needing the NOT, the ZERO and the ONE. These are the ULMs I want to
distinguish from the more ordinary ones.

Candida
---
Candida Ferreira, Ph.D.
Chief Scientist, Gepsoft
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Re: Universal logic modules vs NAND-like modules
On Mon, 16 May 2005 14:42:37 GMT, "Candida Ferreira"

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I've seen them named "complete logic gate set" or "primitive logic
gate set". I am not sure whether there is a universally accepted name.

Re: Universal logic modules vs NAND-like modules

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Do you mean, they are _generators_ for whole family of binary functions ?

MB

PS: there's a booklet by Emil Post on this subject of binary
functions. Forgot the title, sorry.

--
Michel BILLAUD                   snipped-for-privacy@labri.fr
LABRI-Université Bordeaux I     tel 05 4000 6922 / 05 5684 5792
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Re: Universal logic modules vs NAND-like modules
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Yes, exactly like NAND and NOR. Just to give another example, you can also
do that with the function a'c'+b'c.

Candida
---
Candida Ferreira, Ph.D.
Chief Scientist, Gepsoft
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Re: Universal logic modules vs NAND-like modules
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you
need
with
and the
without

Why?


Re: Universal logic modules vs NAND-like modules

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Re: Universal logic modules vs NAND-like modules
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Because with them you can find interesting solutions using just one kind of
gate. I think that, if for nothing else, this might be fun. And if fpga
technology allows people to use different kinds of gate such as the
3-multiplexer, why not use other complex modules? And if you know for sure
the module you are using is a NAND-like module you can even relinquish the
use of inverters and build circuits using just that gate.

Candida
---
Candida Ferreira, Ph.D.
Chief Scientist, Gepsoft
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Re: Universal logic modules vs NAND-like modules

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True. NCR once produced a computer using only NAND gates.

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A four to one mux can make any boolean function of two variables.
The mux selector takes the two inputs and the mux inputs
become a function code.

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A NAND or NOR is the simplest case, but requires multiple instances.
A 4:1 mux is the simplest complete case for two inputs.
There are cases in between and redundant cases,
but those are not very interesting.

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Not in digital electronics. Do some research on "Lattice Theory"


         -- Mike Treseler


Re: Universal logic modules vs NAND-like modules

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other

It's a good bet that they didn't use any NAND gates to generate
ones or zeroes!  This sounds like a mathematician kind of question
rather than engineering...


Re: Universal logic modules vs NAND-like modules

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A rose by another name.

I read NOT,   ZERO, and ONE as
inverter, tied low, tied high.

          -- Mike Treseler


Re: Universal logic modules vs NAND-like modules
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Someone needs to tell me how to create a one or zero using only NAND
gates.

The only thing I can think of would be to use two gates in a loop.
This will have two stable states, 1-0 and 0-1.  The two free inputs
will set the gates to the two states when taken low since any input at
a zero will make the output of the gate a one.  One of these free
inputs is tied to its twin input to make an inverter.  The other is
tied to its own gate output.  If the gate output is a one, it causes no
action on the gate and is stable.  If a zero, it will cause itself to
become a one and be then be stable.

But this will only generate a stable output after some period of time.
Not exactly my idea of a useful circuit.


Re: Universal logic modules vs NAND-like modules

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any
at
no
time.


This is why I said the problem was mathematical and not engineering.
A Boolian NAND gate performs a truth function on ones and zeroes only.
This is not the same as a Verilog NAND gate which can take X or Z
as well as 1 or 0 and produce X as well as 0 or 1.

The Boolian NAND also does not imply a time delay.  So given such a
gate with an unknown input "A", you can produce the inversion of the
unknown input "A_BAR" (A NAND A), and then create 1 by NANDing "A"
with "A_BAR" (A NAND A_BAR).
Zero requires an additional inverter (1 NAND 1).

In the real world this would produce glitches whenever "A" changed
state.


Re: Universal logic modules vs NAND-like modules

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[nand]
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In the real world, who needs to get 0 and 1 from whatever gate anyway ?

BTW, this reminds me of a funny paper on how to build a triple not
circuit using only 2 not gates (and a number of and- and or-
gates).

MB



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--
Michel BILLAUD                   snipped-for-privacy@labri.fr
LABRI-Université Bordeaux I     tel 05 4000 6922 / 05 5684 5792
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Re: Universal logic modules vs NAND-like modules

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Not desperately needing it, but anyway:

         x nand (x nand x) =  x nand not(x) = 1
and then
        [x nand (x nand x)] nand [x nand (x nand x)] = 0


MB



--
Michel BILLAUD                   snipped-for-privacy@labri.fr
LABRI-Université Bordeaux I     tel 05 4000 6922 / 05 5684 5792
We've slightly trimmed the long signature. Click to see the full one.

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