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 Forum index » Clavia Nord Modular » Bugs
Clockdivider outputs hi logic on negative edge
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Fozzie



Joined: Jun 04, 2004
Posts: 875
Location: Near Wageningen, the Netherlands
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G2 patch files: 49

PostPosted: Sat Aug 27, 2005 1:46 am    Post subject: Clockdivider outputs hi logic on negative edge Reply with quote  Mark this post and the followings unread

Please notice the patch that is attached. Note how the clock divider outputs a logic high when the value on its input changes from 64 to 0, that is the negative edge. It should be the positive edge.

This can be a problem when triggering things by manual keystrokes or midi notes with fixed length; the triggering now occurs on key release / note end, which can result in all kinds of timing problems.

NOTE: when the toggled mode is in the upper position, it works just fine. See patch for the bug when the toggled mode is in its lower position.


Clckdivider edgebugtest.pch2
 Description:
Patch to test the edge behaviour of the clock divider module. Hit the switch manually to make positive or negative edges.

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 Filename:  Clckdivider edgebugtest.pch2
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Fozzie



Joined: Jun 04, 2004
Posts: 875
Location: Near Wageningen, the Netherlands
Audio files: 8
G2 patch files: 49

PostPosted: Thu Sep 22, 2005 3:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Rob wrote on the list:
Quote:
There is no bug but rather an ill-documented feature, as the helpfile and
manual give wrong information. When in "Toggle-mode" the ClkDiv module does
not only toggle on a 'positive going' zero crossing but also on a 'negative
going' zero crossing. It works like this: after a reset the output starts at
a high level, then the ClkDiv will toggle when the clock goes either from
low to high or from high to low.

The module is actually designed to work that way, but that it is meant to
work that way was apparently not relayed to the person who wrote the first
version of the helpfile and manual.

The advantage of the ClkDiv working this way in toggle mode is that one can
also have divisions by 1.5, 2.5, 3.5, etc. These are of particular musical
interest, both for audio frequencies (1.5 give a quint below the pitch) and
rhythm (e.g. to divide to triplets).

Beware: in the DEMO software the ClkDiv in toggle mode IS buggy. In fact in
the demo software the module immediately goes berserk in toggle mode and
shouldn't be used in that mode. On the hardware however it should work
exactly as described above.

To get the behaviour of a 'true digital logic divider', like made with a
4013 or 4024 CMOS chip, one can use the flipflop module like one would use a
4013 chip or the binary divider module for a 4024.

in the same direction, lots of persons bottoms get wet, but the fire will
not be extinguished. Wink. So, chaining the SR8 and SR32 do need an extra
'bucket' in between.)
In the BeMused patch an eight input switch is used to select either a
divided clock from seven available division rates or the output of a SR32
shift register module.
E.g. in the Muse there are clock division rates of 3, 6, and 12. These can
be made by using the ClkDiv in toggle mode and set it to 3, which will
divide the basic clock by 1.5 (three zero crossings in whatever direction).
Then the binary divider module can be used on that divided by 1.5 signal to
get the divisions 3, 6, 12, 24, 48, 96, 192 and 384.

Btw, you might want to take a look at the patch 'BeMused', that I think is
in the factory set or else should hang around somewhere on
electro-music.com. This patch contains a pattern generator modelled after
the Muse.

For those that do not know the Muse, it was a self-contained musical pattern
generator box built in the second half of the seventies. It has two sets of
four long slide switches. Each slide switch is in fact a 44-position switch.
44 single bit signals are generated by clock dividers and a long shift
register. Each slide switch selects one of these 44 signals. the first four
slide switches form a four bit combination from which a single parity bit is
generated. This parity bit is fed back into the shift register to create
'ever changing patterns', well in fact 'pseudo-random' patterns. The second
set of four slide switches is used to select four bits that lets the box
play one of sixteen notes. The notes are selected from e.g. a major chord.

In the BeMused patch one will find a nice G2 solution for the long Muse
shift register, instead of using four SR8 modules that would take 32 outputs
and so a lot of memory and lots of switch modules, four SR32 modules are
used in parallel, to sort of mimic a slide switch for the particular bit.
Saves a lot of module output memory and avoids having to use buffer S&H
modules clocked at an inverted clock between SR8 modules. (Note that the SR8
and SR32 modules are basically bucket brigades, where one always needs twice
the amount of persons minus one person than there are available buckets,
e.g. if there are as many persons as buckets, and all turn at the same time

/Rob


Bug, feature....what's in a name Razz. I guess this one's cleared, only the documentation in helpfile/manual needs to be changed.
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Blue Hell
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Joined: Apr 03, 2004
Posts: 22225
Location: The Netherlands, Enschede
Audio files: 208
G2 patch files: 319

PostPosted: Thu Sep 22, 2005 9:07 am    Post subject: Reply with quote  Mark this post and the followings unread

Thats some new light.

The muse patch Rob refers to is at http://electro-music.com/forum/topic-2035.html

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