AW: Re: Analog Sequencer Poll

[Tony Clark]

> As a newcomer to this list, I've been following this discussion with
> some interest. I can't resist asking any longer: is there any
> *particular* aversion to the use of micros amongst the members of this
> list? I mean, after all: a micro can do all a 4017 does - it's just a
> matter of "coding" in silicon vs. coding in solder.
> 
> I ask this because this seems to me the PERFECT place for a micro of
> the 20 pin, low power variety. Attach it to a pair (or more) of analog
> MUX's, and you got a very flexible sequencer. In fact, I did just this
> to build a programmable waveform generator. It has eight steps/wave, a
> programmable output filter (just for waveshape smoothing) and TWO
> outputs, with tightly controlled (adjjustable) phase between the two.

   Well I'd imagine that the number one reason that we don't want to go 
this route simply would be that CPU's come and go.  What is there to 
assure that the special chip you use will still be in production years 
from now?  TTL/CMOS will be with us forever.  :)
   Using only TTL or CMOS technology keeps the overall design simple.  
Simple enough that everyone shouldn't have any problems working with the 
circuitry, modifying it how ever they want to. amd troubleshooting it in 
the event something does go wrong.
   Besides, I seem to recall the large debate that went on about DSP 
chips.  Everyone has their preference.  Using a special chip might lead 
to some unhappy camper.  :)  This way, no one will complain (unless you 
simply botch up the design).

> Alternatively, has anyone considered using a 74AHC283 instead of a
> counter? This is a four bit ALU and "accumulator" on a chip. By
> controlling the four data input lines and the five ALU control lines
> (three for op sel, carry in, carry out, etc) you can pretty easily get
> "random" steps, or "skips" or go up or down or....

   The chip possibilities are limitless.  :)

   Tony

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I can't drive (my Moog) 55!
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Tony Clark -- clark at andrews.edu 
http://www.andrews.edu/~clark
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