A viable solution[Was]Re: MM5837?

[patchell]

Harry Bissell wrote:

> Remember you need a mechanism to unlatch the generator from an all 1's
> (or 0's depends on logic) state, should this occur. Eventually (i think) the register
> will reach this state.  The schematic I've posted in the past has an RC network to
> kick in a pulse if the time-out is reached. I have NEVER heard this audibly...
>
> H^) harry
>

    This would not be a big deal.  Under normal operations, the shift register will not get
into the all '1's state, however, external influenes (electrical static, ground glitches,
EMP) it might be posisble to have this happen.  It would be easy to add in circuitry to check
for all 1's and reset it back to zero.

>
> patchell wrote:
>
> >     Here I am listening to my chugga chugga (I found it, didn't even have to do so by
> > inspection, I just listened to it, it is a whole lot worse than I remember), and a good
> > solution to this problem is staring me right in the face.
> >
> >     If you would all please turn to page 147 in the good book (Digikey-July-Sept 2000),
> > you will notice that the XC9536-15PC44C is only $3.30 in unit quantities.  It would be
> > entirely posible to put a 32 bit shift reg and XOR feedback into one of these little
> > suckers.  I just have to dig up the article I have stashed somewhere that shows which
> > cells to tap.  About a half hour at Xilinx Foundation, and I should have a hex file.
> > (Although, I will not be back at work until this Wedensday).  I would post the hex file
> > and schematic (and encourage others to post it on their site).
> >
> >     Anybody interested?
> >
> >     -Jim
> >
> > Harry Bissell wrote:
> >
> > > Likewise I have a schematic for one that I adapted from Popular Electronics.... and
> > > used
> > > in the Prophet V to replace the... (gawdawful) ... chugga chugga unit ! will send
> > > scan to
> > > any who requests...
> > >
> > > H^) harry
> > >
> > > Magnus Danielson wrote:
> > >
> > > > From: patchell <patchell at silcom.com>
> > > > Subject: Re: MM5837?
> > > > Date: Sat, 02 Sep 2000 12:22:18 -0700
> > > >
> > > > >     All I can say is, good luck.  In one of my home made synths, I am pretty
> > > > > sure I have one of these things.  You might be able to talk me out of it as a
> > > > > last resort (I personally don't really care much for it, you can hear it
> > > > > repeat, if you listen really carefully).  These went out of production a long
> > > > > time ago.  Keep me posted if you can't find one.
> > > > >
> > > > >     -Jim
> > > > >
> > > > > Romeo Fahl wrote:
> > > > >
> > > > > > Hello,
> > > > > >
> > > > > > I'm looking for an MM5837 ("Chugga Chugga") pseudo-random noise IC to do
> > > > > > some experimenting with.  Does anyone have a spare or know of a source for
> > > > > > one?
> > > >
> > > > Do you really require the MM5837? It is not too complex to cook up a noise
> > > > source out of standard CMOS or TTL. If you go to the archives (Oh, I never
> > > > thougth I would refer to them!) you will find a thread on the subject, I recall
> > > > being part of it, I even posted a ASCII schematic in there...
> > > >
> > > > If you really want a a 17 stage noise source it should not be too difficult to
> > > > make an equalent schematic, but a longer shifter is better. A 4006, a XOR gate
> > > > of choice and some clock generator (two of the XOR gates could be used for
> > > > that) and you have an equalent.
> > > >
> > > > The MM5837 is a 17 bit shift register with feedback at the 14th tap. The MM5837
> > > > also has an internal oscillator which changes frequency with the supply power
> > > > (obviously!). Getting something equalent should not be too hard. Actually,
> > > > a 17-tap shift register is a bit too short... it will beat too obviously.
> > > >
> > > > Anyway for some more info, check out:
> > > > http://www.vego.nl/8/18/8_18.htm
> > > > http://www.io.com/~ritter/NOISE/NOISRC.HTM
> > > >
> > > > Cheers,
> > > > Magnus
> >
> > --
> >  -Jim
> > ------------------------------------------------
> > * Visit:http://www.silcom.com/~patchell/
> > *-----------------------------------------------
> > *If you didn't buy a home in Santa Barbara,
> > * You didn't pay enough!
> > ------------------------------------------------

--
 -Jim
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* Visit:http://www.silcom.com/~patchell/
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