Re: The death of combinatorial logic.

Tim Polmear <polmear@xxxxxxxxx> wrote:
Not wanting to spend $40 bucks a robot on UCN5804B controllers I
thought I'd make a controller with FETs and discrete logic, using the
circuit from kitsrus.com. It was only as I started laying out the
tracks for the AND gates to modify the circuit so that it could idle
without running power through the power FETs that I thought "This is
crazy, 6 ICs to do the job of 2. I can run these FETs straight from a
PIC".

So I ditched the XOR gates, the AND gates and the NAND gates with
Schmitt triggers and designed the circuit round a single PIC that I'll
get running with software.

Now what do I do with all my chips?

I only recently started looking into microprocessor technology because of a
new interest in robotics and was amazed to find how powerful and cheap the
embedded processors are now. It was back in the day of the 6800 and Z80
that I was last paying any attention to the hardware. When I saw how
small, and cheap, and simple they were now, I too had the same thought that
there's little point in using digital logic gates in typical circuits
anymore. You can buy a complete computer on a chip for less than 10 bucks
and write software to replace hundreds of digital gates and components.
And they are programmable so you can easily change the design without
changing the hardware.

I had another similar experience about 10 years ago when I started to
design custom hardware for doing DES hacking just for the fun of it. After
working out the timing with TTL gates, I realized that the custom TTL
hardware wouldn't be able to run any faster than a well optimized software
implementation on a PC. The PC processors even back then were so well
optimized and pipelined that they could outperform hard wired TTL gates.
Yet another realization how times were changing.

--
Curt Welch http://CurtWelch.Com/
curt@xxxxxxxx http://NewsReader.Com/
.

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