User manual
4
is high, the resulting signal B will be logic 0
(button unlit), and it will mask bit #7 so that
the resulting bit (available at the Leibniz head-
er/bus) will be 0 regardless of the input state
of this bit. The same masking of bit #7 occurs
when the gate signal is inactive (0V), and is
not manually inverted. note: masking all bits
of the data (all buttons unlit) results in Gera
not passing any data to its Leibniz out. This is
in contrast to another Xaoc Devices module,
Lipsk. In Lipsk, all buttons unlit indicate that
the data is passed through unchanged.
EFFECT OF MASKING BITS
Data processed by the Leibniz subsystem mod-
ules may represent voltages or waveforms. For
example, combinations of 8 bits represent 256
different values from 0 (binary 00000000) to
255 (binary 11111111), which are abstract in
the digital domain but may be converted to a
range of voltages by a DAC. What happens if a
bit is masked (i.e., it is forced to be 0)? The set of
256 values is reduced because each of the two
original values that differ only by this bit will be
“glued” into one value with this bit equal to 0.
For example, observe that 2 (binary 00000010)
and 3 (binary 00000011) differ by the lowest
bit. Actually, all even and odd values differ by
the state of this bit. Thus, masking the lowest
bit will not change any even value but will con-
vert all odd values to even; therefore, the set
of possible values will shrink from 256 to 128.
Masking more bits from the bottom end up re-
duces it even further. For example, masking the
lowest four bits leaves only the four upper bits
active, which results in 2
=16 possible combi-
nations, from 0 (binary 00000000), through 16
(binary 00010000), 32 (binary 00100000), up
-
ing the number of possible values is called quan-
tization. Indeed, connecting Gera in a loopback
of Drezno’s ADC and DAC and turning some of
the lowest bits off allows one to create a crude
quantizer. Passing a variable waveform through
this setup results in a stepped waveform at the
Masking high bits also reduces the set of val-
ues, but the impact on waveforms differs. Ob-
serve that all values greater than 127 have the
11010101) because this bit represents a value of
2
7
=128. Masking this bit will not affect any val-
ues lower than 128 but will subtract 128 from
higher values; for example, 213 will be changed
input a input b output
0 0 0
0 1 0
1 0 0
1 1 1
data processing in gera logical ‘and’ truth table
AND
LED
INV
toggle
button
gate
input
a
b
8x