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Fig.
13-19
Video
control
circuit
(2)
Audio
control
circuit
Muting
of
external
stereo
audio
inputs
is
switched
on and
off
by
this
circuit.
Left
and
right
channel
muting
signals
(LMUTE
and
RMUTE)
are
generated
by
output of
VCON
register bit
7
write
and
PPI
PC
port
bit
4
(PC4).
To
latch
PC4
by
using
the
LMUTE
leading
edge
during
right
channel
muting
control,
LMUTE
has
to
be
changed
from
L
to
H.
An
integrating
circuit
(R319/C305)
is
used to prevent response
in
the
left
channel
muting
circuit
(Q303/Q305)
during
this
L
-+
H
change.
And
to ensure equal
response times
in
both
left
and
right
channels,
an
integrating
circuit
(R320/C306)
is
also
included
in
the
right
channel
muting
circuit
(Q304/Q306).
•
Left
channel
MUTING
ON/OFF
W/m
\V//m
77777777,
•
Right channel
MUTING
ON/OFF
pc
«
7M
\
ww/m
_
I
mw,
'/M
1
mMzmmzzm
i
mm
RCH
Fig.
13-20
CPU
ASS'Y
ANALOG
ASS'Y
87
Fig.
13-21
Audio
control
circuit
and
timing
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