[sdiy] ...dumb question (CD4017 sequencer)

[phillip m gallo]

Haven't done the 4017 sequencer in decades but if memory serves.  You stop
at a stage by Stopping the Clock.  The output from the step you want to stop
at is used to "gate" the clock by driving INHIBIT.  If you want to restart
the sequence you have the last step drive the RESET ( which will
automagically remove INHIBIT as the step which gated the clock is no longer
asserted.

I used to cascade them and never had to use fancy logic just a VC clock for
the 4017 input and patch matrix for routing steps to RESET and INHIBIT.

regards,
p


-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of John Blacet
Sent: Monday, September 30, 2002 7:30 AM
Cc: Synth DIY
Subject: Re: [sdiy] ...dumb question (CD4017 sequencer)


"How do you get the sequencer to stop so that it - A) does not put out
the voltage of the current step and B) always starts again
on step 1, when you restart it?"

---Well "A" is not a "normal" sequencer function in most cases. When you
stop a sequencer, it usually puts out the step voltage. The desired
silence is typically a function of turning off the VCA in a patch (via a
gated ADSR, for example). So you may wan tto think of having a gate out
if you don't already.

You *could* use an analog switch connected to the seq out and control it
via the seq start/stop to remove any voltage out when the seq is
stopped.

Having the 4017 *reset on start *requires a bit of external logic
between the start/stop and the 4017 reset pin. You might want to try a
very short pulse from the rising edge of the "start".

While the 4017 looks like a sequencer on a chip, getting it to do the
usual seq functions is a bit complicated. You will probably find some
circuits on the web if you do a search.

--
Regards,
--/////--
John Blacet
Blacet Research
http://www.blacet.com


---
Incoming mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.391 / Virus Database: 222 - Release Date: 9/19/02

---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.391 / Virus Database: 222 - Release Date: 9/19/02