Re: OT: Riddle for the bright minds here

From: Androcles (androc1es_at_nospamblueyonder.co.uk)
Date: 06/11/04 

Date: Fri, 11 Jun 2004 10:57:26 GMT

"sal" <believer@nospam.org> wrote in message
news:c3b1113922bb94f09466e42d5604d2a1@news.teranews.com...
| On Thu, 10 Jun 2004 23:04:43 +0000, Androcles wrote:
|
| > |
| > | Yes but that last line is important. You can build all the logical
| > | operators, including 'not' and 'or', out of 'xor' and 'and'.
| >
| > You can build XOR out of NAND, which were the early and most common TTL
| > gates, 4 to a chip. NAND lent itself readily with TTL. High voltage at
the
| > base is low voltage at the collector.
| >
| > | That isn't
| > | true of 'or' and 'and', just because that last line is different.
| >
| > Sure you can, but that is wasting the gates and slows the system. Tie
one
| > input of a NAND gate to high...
|
| But that's a NAND gate, which incorporates a NOT. As I said, you can't do
| it with plain AND and OR, afaik. There's no way to make NOT with them.

I didn't deny it, did I?
I was just being practical, that's all.

|
| XOR and AND => you can make the complete set
|
| AND and NOT => you can make the complete set
|
| OR and NOT => you can make the complete set
|
| NAND alone => you can make the complete set

Lovely, isn't it? There is beauty in that. Edge-triggered flip flops out of
NAND. voila! memory! Half-adders out of NAND. Arithemetic!

|
| Just AND and OR => you need a separate NOT gate
|
| But AND gates are kind of unphysical, aren't they?

Is that Sirvent the Unscientific unphysical or physically unphysical?

Real gates are
| almost always NANDs, not ANDS. (Or has that changed with the advent of
| whatever magic they use to drive chips at 2+ GHz? I'm pretty out of
| date on the hardware end of things...)
|
|
| --
| To email me directly, take out nospam and put back physicsinsights

I think you can still get them at Radio Shack. AFAIK, the principles of
Boolean Algebra haven't changed even if the technology has.
Androcles

Relevant Pages

  • Re: NAND Gates Rule!
    ... With a million XOR exclusive OR gates, nobody can build one NAND ... | Energy is power multiplied by time. ... NAND FLASH HEADLINE: ...
    (sci.electronics.basics)
  • Re: Interview Embedded Software Questions
    ... of the minimum number of NAND gates. ... Off the top of my head, I'd say that three gates are needed ... It depends on whether or not the inverses of the input signals are ...
    (comp.arch.embedded)
  • Re: OT: Riddle for the bright minds here
    ... > You can build XOR out of NAND, which were the early and most common TTL ... NAND lent itself readily with TTL. ... High voltage at the ... but that is wasting the gates and slows the system. ...
    (sci.physics.relativity)
  • Re: NAND Gates Rule!
    ... With a million XOR exclusive OR gates, nobody can build one NAND ... Neither AND NOR OR equals the full power of the NAND. ... Money is the energy of imagination divided among the knowledgeable. ...
    (sci.electronics.basics)
  • Re: building boolean gates
    ... NAND and NOR gates can be used to build any logic function. ... You can build any logic function out of XOR gates. ...
    (sci.electronics.design)