Xaoc Devices ERFURT User manual

binary phase
akkumulator
Model of 1989
operator’s manual rev. 1989/X2/1.0
ERFURT ThE lEibniz binaRy sUbsysTEm

salUT
Thank you for purchasing this Xaoc De-
vices product. Erfurt is a bi-directional
digital counter, frequency divider, and a
component of our 8-bit Leibniz Binary
    
the output of the counter may be used as
a phase source driving a digital wavet-
able, connected to other Leibniz modules
it may scan waveshapes in Jena, produce
stepped voltages useful for making in-
teresting glissandi with Drezno and any
VCO, generate gate patterns animating
the spectrum of Odessa harmonic banks,
spawn pseudo-chaotic sequences when
fed back to Lipsk, etc.

other Leibniz components), and act as
an 8-output clock and audio frequency
divider.
Since Erfurt is based on CMOS logic (no
CPU!), it can be clocked at very high fre-

any aliasing or frequency interference.

source that may be used with clockless
data sources.
insTallaTiOn
The module requires 6hp worth of free
space in the eurorack cabinet. Always
turn the power off before plugging the
module into the bus board using the sup-
plied ribbon cable. Pay close attention to
power cable pinout and orientation. The
red stripe indicates the negative rail and
should match the dot or –12V mark on
the bus board as well as the unit. Erfurt
is internally secured against reversed
power connection, however, rotating the
16-pin header may cause serious dam-
age to other components of your system,
because it will short circuit the +12V and
+5V power lines. Always pay particularly
close attention to the proper orientation
of your ribbon cable on both sides!
Besides power, you may want to connect
Erfurt to other components of your Leib-
niz Subsystem (unless you intend to use it
standalone). Erfurt comes with one 10-pin
ribbon data cable to connect with other
Leibniz modules alongside any additional
cables included with other modules in the
subsystem. The 10-pin unshrouded header
labeled out is where you need to plug the
cable that goes to the in header of your
      
Odessa). The incoming data from a module
preceding Erfurt (e.g. Ostankino, Drezno,
Lipsk, etc.) should be plugged into the 10-
pin unshrouded header labeled in. Please
observe the marks of pin #1 (red stripe) on
all connected modules. Depending on the
intended use of Erfurt, these connections
may not be necessary. We advise you to
plan ahead as to how you wish to incorpo-
rate Erfurt into your modular setup.
A jumper labeled clk src selects wheth-
er Erfurt runs with its own internal clock
generator or uses the clock signal delivered
with the Leibniz data. Put the jumper in
the int position when there is only a stat-
ic data source (e.g. Lipsk or Ostankino), or
when you don't feed Erfurt any data via the
Leibniz interface. Set the jumper to ext
when the preceding module delivers clock
alongside its data (usually changing over
time), like Drezno or Jena.
2
module
explained

note: do not plug a power cable to
the leibniz headers. This will destroy
your unit and may also jeopardize oth-
er Leibniz modules connected to it! The
module should be fastened by mounting
the supplied screws before powering
up. To better understand the device, we
strongly advise the user to read through
the entire manual before use.
mOdUlE OVERViEW

1. As with other modules from the Leib-
niz series, Erfurt features a bank of eight
binary outputs 1producing 5V gates,
where an active gate signal represents
logic 1 and an inactive gate represents
logic 0. There are eight corresponding
yellow LEDs 2that display the activi-
ty of individual bits of the digital num-
ber indicating the internal state of the
counter.
The two push buttons allow for manual
incrementing 3and decrementing 4
of the state (increasing and decreasing

state can also be reset to zero by simulta-
neously pressing both buttons. There are
three clock inputs for incrementing 5,
decrementing 6and resetting the state
7. All inputs accept arbitrary modular
signals (including those of audio rate and
above), but are best fed with clocks, gates
or triggers.
The two switches allow the Leibniz clock
to drive the counter when there is noth-
ing plugged into the incr clock input
5
. The leftmost switch 8turns the Leib-
niz clock on and off, and the rightmost
3
front panel
overview
1
2

5
6
7
9
3
4
8

4
switch 9offers three frequency pre-scal-
ing options: 1:256, 1:1, and 1:64K (in oth-
 
      -
imately 2MHz, this yields about 7kHz
(high audio rate) in the upper position
and about 28Hz (LFO rate) in the lower
position. note: The switches have no ef-
fect when you plug your own clock to the
input 5.
PRinciPlE OF OPERaTiOn
        
register that holds the internal state of
the machine and an adder that combines
the internal state with the incoming
data value. At every rising edge of the
clock signal, the output of the adder is
written back to the register. The choice
of the clock input (incrementing or dec-
rementing) decides whether it is a sum
or difference, though two clocks may be

-
ing clock has higher priority.
The Leibniz clock that arrives together
with the data through the ribbon data
cable may be used to drive the counter
when you set the leftmost lbz clk switch
to the on position. Since this clock is of-
ten very high frequency, it may be conve-
niently pre-scaled by 1:256 or 1:65,536
via the rightmost switch. This (divided
or not) Leibniz clock is always used for
counting up, therefore it is normalled to
the incr clock input and is replaced by
anything patched there.
Erfurt also features an internal high
frequency (near 2MHz) clock (selected
using a jumper at the back) that is useful
when the unit is operating standalone or
connected to a static Leibniz data source
like Lipsk (provided nothing is connected
to Lipsk's Leibniz in header).
The Leibniz out header at the back taps
directly from the adder before the data is
written back to the register. This allows
Erfurt to pass the potentially quickly
changing data to subsequent Leibniz
modules in the chain (e.g. samples of a
signal from Drezno to Jena). The data is
being offset (modulo 256) by the content
of the register regardless of whether the
content stays still, is updated slowly or
rapidly (according to the clocks plugged
into the front panel jacks), or is being ad-
justed manually.
cOUnTER Vs FREQUEncy diVidER
When Erfurt is operating without any
Leibniz data source, the in header at the
back should be left unplugged. There is a
normalization on the header, enforcing
the value of 1 (binary: 00000001) being
fed to the adder. Therefore, Erfurt chang-
es its state by 1 at each impulse from the
clock input so that it counts from 0 to 255.
    
       -
ates modulo 256. Obviously, with a clock
plugged into the decrementing input, Er-
furt similarly counts down from 255 to 0.
Taking signals out of the individual bit
jacks offers the clock frequency divided
by 2 (bit 0), 4 (bit 1), 8 (bit 2), 16 (bit 3),
32 (bit 4), 64 (bit 5), 128 (bit 6), and 256

is a classic octave frequency divider.

5
block
diagram
With two different clocks patched to the
inputs, the counter alternately increases
and decreases its state, and ultimately
counts with a rate proportional to the
frequency difference between the clocks.
GEnERaTinG mORE cOmPlEX
PaTTERns
When there is a Leibniz data source con-
nected at the back (even one as simple as
Lipsk), the state of the counter may in-
crease or decrease in larger steps, depend-
ing on the data present at the Leibniz bus
(e.g. the value programmed by the Lipsk
      -

      -
     
        
octave dependence between rates of indi-
vidual outputs is no longer valid.
When the decr clock input is used and
certain non-trivial input values are pro-
grammed with Lipsk, Erfurt becomes a
generator of intrinsic rhythms that may
be recognized from dance music genres.
-
   -
ious divisions of the common length by
different integer factors. These divisions
have remainders that contribute to in-
spiring off-beat incidentals, not unlike
the popular Euclidean rhythms. The rule
of thumb is that most elaborate rhythms
occur when 256 does not divide evenly
by the input value N, and the remainder
has several non-zero bits or is a prime
      
N=00011011 (which is an 8-bit equiva-
lent of 27) is not an integer divisor of 256.
The remainder is 00001101 (which is an
8-bit equivalent of 13) – a prime number.
Thus, this combination of bits yields an
interesting rhythm.
Σ
leibniz
data bus
Selectable
via jumper
Clock source
int
ext

Output
Bit outputs

register
÷64k
÷256
leibniz
data bus

mathematical
or musical?
6

sequences of bits may be obtained by
    -
ry outputs to the inputs of the module

such a scenario, the increment value for
each consecutive step is being modulat-
ed (in a nonlinear way!) by the previous
Erfurt counter state.
Such dependence sometimes yields sim-
ple cyclic behavior, but it may also pro-
duce a pseudo-chaotic sequence. The
     
bit 0
bit 1
bit 2
bit 3
bit 0
bit 1
bit 2
bit 3
mathematical clock division musical clock division
When a binary counter counts upwards
with an increment of 1, the cycle at each
       
half, and proceeds to logic 1 in the sec-
      
(going back from 1 to 0) causes the out-
put directly above to advance by half a
       
is binary 00000000, and the last is bi-
nary 11111111, which is called mathe-
matical division. After the very last state
(11111111 is an 8-bit equivalent to 255)
the return to 0 of the lowest bit spawns a
quick transition to 0 of all the bits above it.
Counting downward (with a decrement-
ing clock) reverts the situation: at each
output, the cycle starts with logic 1 and
        
3b). Each completed cycle (going back
-

state of the counter is binary 11111111,
and the last one is binary 00000000,
which is called musical division. After the
very last state, the jump to 1 of the lowest
bit spawns a quick transition to 1 of all
the bits above it (transition from binary
0000000 to binary 11111111).
Erfurt offers both options thanks to its two
clock inputs that are active simultaneous-
decr clock
input you get a very straightforward 4/4
rhythm on 8 levels (e.g. from 1/32nd up to
4 bars if your source clock corresponds to
1/64ths). Also, if there is any slip in the se-
quence, you can nudge it forward or back-
ward by using the decr and incr push
buttons respectively.

erfurt
patch sideas
7
with one Erfurt is 256, but if your goal
is total chaotic madness, it may be dis-
rupted by feeding more data to the Leib-
niz in port of Lipsk.
PaTch idEas
-

as a source of Leibniz data. Each Mosk-

value corresponding to the position of
the CV potentiometer. Connect Ostanki-
   out to Erfurt's Leibniz
in    out   in
out
in
the division to 1:256. This will produce
a digital stepped ramp in Erfurt (so-
called phasor) which can be wavesh-
aped and modulated by Jena and con-
verted to an audio signal by Drezno.
Set Jena to asynchronous mode to
obtain nicely aliased waveforms result-
ing from the skipped samples. Use syn-
chronous mode for cleaner results.
note: Moskwa will affect the pitch lin-
early (not V/oct).
        
Lipsk followed by Erfurt (whose Leib-
niz output is then fed to the input of
Drezno) you may generate interesting
CV glissandi that can drive a VCO. Use
an LFO to clock the steps and program
the width and direction of the steps
    
      -
multaneously. To limit the length you
can use feedback from a selected bi-
nary output of Erfurt connected to its
own reset input. You can also limit the
-
sion by patching dummy cables into the
bit inputs to make the quantization
steps wider without affecting the speed
of the glissando. Alternatively, you can
unlink the normalization in Drezno,
and patch only a few of the highest bit
inputs to the front panel.
      -

 
the out     
Leibniz in header, and activate Odes-
     
voices button until it starts blinking.
Remember that the effect very much
     
number of audible overtones.
-
ety of rhythmic patterns that may trig-

you can also try the special drum bank
in Jena. Please consult the pattern guide
available on our website (Jena shapes
chart). For the best results, use Jena's
synchronous mode and special drum
bank e. Connect Lipsk to Erfurt and
then Erfurt to Jena and use the individ-
ual bit outs from Jena as triggers. With
the Leibniz clock divided by 64K, the
value programmed on Lipsk will be your
tempo multiplier.
accEssORy
Our Coal Mine black panels are available
for all of Xaoc Devices modules. Sold sep-


main
FEaTUREs
Leibniz Binary
Subsystem
component
Phase
accumulator
Programmable
digital oscillator
Bi-directional
binary counter
Clock and
audio frequency
divider
TEchnical
dETails
Eurorack synth
compatible
6hp, skiff
friendly
Current draw:
+25mA/-30mA
Reverse power
protection
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EASTERN BLOC TECHNOLOGIES MADE IN THE EUROPEAN UNION
ALL RIGHTS RESERVED. CONTENT COPYRIGHT © 2022 XAOC DEVICES. COPYING, DISTRIBUTION, OR
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