Roland JUNO-106 - Circuit Details; Waveform Generation ICs; Integrated Circuit Information; VCF and VCA Circuitry

JUL. 31, 1984
WAVE GENERATOR
1/2MC5534A (C4, 8, 12)
MC5534 (IC 4, 8 and 12) is, with a given rectangular at CLK IN, capable of
generating three different waveforms; divided by two rectangular, sawtooth
and variable-width rectangular (Pulse Width Modulated). There are three
versions in MC5534 series; of these MC55344A is the latest version containing
complete two identical circuits. See Parts Change Notes in the Parts List
section for detail.
SUB OSCILLATOR
This is self-explaining from the figure. The output amplitude being variable
to a change of collector supply voltage (SUB LEVEL).
SAWTOOTH
For sawtooth and PWM waveforms, DCO CV is applied from the slave CPU in
addition to DCO output.
The
DCO
CV
will
keep
the
sawtooth
and
pulse
amplitude
nearly
constant
(approx.
12Vp-p)
over
the
frequency
range
(detailed
Jater).
Therefore,
DCO
CV
includes
LFO,
BENDER,
PORTAMENTRO
and
TUNE
data
as
well
as
key
value,
but
it
does
not
contain
RANGE
data;
the
DCO
CV
sees
RANGE
at
the
output
of
4052
(1C2,
6
or
10)
which
selects
among
R85,
86
and
87
in
accordance
with
RANGE
code
(PF6
and
7
of
the
slave
CPU).
The DCO
CV
charges
C54 through
R85
(if 16’) and
discharges
through
transistor
E
on
the
positive
going
edges
of
DCO.
If
the
RC
time
constant
(C54
and
R85,
86
or
87)
remains
unchanged,
sawtooth
amplitude
becomes
low
at
4’,
The
same
principle
applies
to
key
range
over
the
keyboard;
the
output
amplitude
de-
creases
as
the
note
runs
high.
Therefore,
DCO
CV
is
made
to
become
higher
in
proportion
to
key
number.
PULSE MODULATED WAVE
At ICB input, sawtooth wave is compared with PWM CV that determines the
pulse duratation of ICB output; duty ratio is 50% at +6V PWM CV and 95%
at +0.6V. With PWM OFF, PWM CV is —0.8V; this can swing and keep ICB
output to High, disabling the rectangular.
VCF, VCA
A1QH80017A is a one-chip VCF and VCA. Both VCF and VCA are indivi-
dually controlled by the several parameters integrated into one voltage: VCF
CV contains CUT OFF (VCF) frequency, ENV, LFO, Key follow and Bender;
VCA CV includes ENV and GATE.
JUNO-106
IC DATA
uPD7810G/uPD7811G
x10 Ks) PET-O/ABIS-6
1s
X20
rco/Tsl O
PCL/RDO SERIAL 1/0
pc2/STKO
wuRT o
PROGHAM
MEMORY:
UR RYTE, DATA
MEMOIY:
(yPLT811) 1986 WYTE:
CONTROL
PORT C
PC3 /INT?2 /TIO
pCa /TUO
PCS-Cl O
PCS/CO0 ©
VCR. COFO
ANT 0
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INSTT.
Ava
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See:
DECODER
AVay O
Pin Configuration
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Block Diagram “ONTO, CUNTROL
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VCF VCA 64k-Bit EPROM
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OUTPUT
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