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SONY
Description of
Functions
1.
System
Configuration
This
silence
data
detection IC
Is
compatible
with the
data formats
of
the
CDL-30, 35 and
40
series
CD-use
LSIs,
and
consists
of
a
silence
data
detection
circuit
(OX- Data),
a
window
generator (OX -Window),
and a
tinner circuit
(OX-Timer)
which
measures
how
long the silence continues.
2.
Function
and
Operation
of
System
Circuits
(1
Silence data detection
circuit
(OX-Data)
The
silence
data
detection
circuit
is
divided
into
two
sections:
a
low-level
detection
circuit
and a
direct
current
detection
circuit.
Simultaneous
detection
of
both the
low-level state
and
direct-
current
state
is
treated
as
detection
of
silence data.
•
Low-
level
detection
circuit:
Detects
whether
the absolute value of the
signal
is
sufficiently
smail.
Since
the
signal
is
two's
complement
data, the
circuit
checks whether
the
upper 12
bits
are
all
O's
or
all 1
's.
•
Direct current detection
circuit:
Detects
whether
the
signal
value
changes. Since
all
bits
up
to
bit
12
are
either
all
O's
or
all
1's, this circuit
checks
only
bits
12 through 16
of
each word
for
each
channel.
Also,
for
reading
in
data,
both detection
circuits
use
the
no-change
edge
of
the
bit-clock
data.
(2)
Window
generator
(OX-Window)
The
window
generator generates the various
latch
pulses
and
ioad pulses
necessary
for
the silence
data
detection
and
timer
circuits.
•
Window
generator
circuits:
These
circuits
generate
the
following
windows and
pulses:
(1)
W1
(Lch,
Rch),
a
load
window
used by
the
low-level
detection
circuit;
(2)
W2
(Lch,
Rch),
a
latch
pulse
used by
the
direct
current detection
circuft:
(3)
W3
(Lch,
Rch), the
silence
data
latch
pulse;
and
(4)
W4
(Lch,
Rch)
the timer
count
load pulse
and
MUT-T
mute
timing pulse.
(3)
Timer
circuit
(OX-Timing)
This
circuit
checks whether
the silence state
continues
for
a
time equivalent
to
1
6,382
samples and
outputs the
muting
signal.
-70-
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