V.
DESCRIPTION
OF
THE
CIRCUIT
OPERATION
5-1
AMPLIFIER
PERFORMANCE
5-1-1
General Description
(1) Functions
a) Input Selec.tor Control
This
microcomputers
is
capable
of
controlling
analog switch TC9164N that
serves
as
the
input selector. Three input systems that.include
PHONO,
CD,
and TUNER, and t,vo monitoring
systems that include TAPE 1
and.
TAPE 2 may
be
controlled.
b) Direct
Access
Volume Control
Reads voltages detected out
of
the sound-volume
touch control through an A/D converter, and sets
the electronic potentiometer in accordance with
the read data. In this process, any designated
setting
will
be
reached from the earlier potentio-
meter position by fading
in
or out.
c) Balance Control
By
setting various level differences between
Leh
and Reh on the main control, up to a maximum
of
30dB
L-R
level offsets may be created.
d) Tone (BASS/TREBLE) Control
Operates the tone control potentiometer
(TC9156P)
in
2dB steps up to a maximum
of
±lOdB, and thereby performs
as
an electronically
.controlled tone circuit. ·
f) Acoustic Pattern Storage
By
this function,. stores in.the microcomputer two
patterns
of
.the tone
control
circuit settings, and
enables the instant loading
of
either
of
the
stored
patterns.
g)
Volume Control Safety Function
With
the touch control operated direct access
. sound volume system that· enables
_the
instant
setting
of
any preferred sound volume level, the
danger exists that the inadvertent touch
of
a
higher position
of
the control will cause a sudden
emission
of
unexpectedly high sounds from speak-
ers.· A time lag measure in the form
of
fade-in's
has beeri provided
to
enable coping with the
above danger, but
as
an
added and positive precau-
tion, this safety function has been added on that
suppresses
all
sounds louder than a
level
set in
advance.
h) TUNER Direct Function.
This·function will set the input selector at TUNER
upon receiving data from the microcomputer.
(Al007T) for the tuner that
is
output
as
soon
as
the tuner has been operated.
5-1-2 Key Input and Dynamic
FL
Display
PIN.
NO
®
®
©
®
®
Strobes
Key
inputs and
FL
displays are both handled dynam-
ically,
and
their basic clock signals generated
by
the
ITMR
interrupt (I ,024
Hz)
for the output
of
strobe
signals.
R4o
R41
I
-4~·~
MAX
12sI1se.:
~~~---------~n
R42
R4
3
R5 o
R5i
Fig.
5-1
5-1-3 Acceptance
of
Key
Inputs
SINGLE PRESSING J i
. 1 I
l I
~
24msec
·
I I I
CONTINUOUS
DEPRESSIONS
---"""'1111111
! I
I
I !L
I I
I I
I I
I
I I
I I
I
....
· :: I
E.
I I
I I
31
IE
31
500ms
150
150
!50
150
!50
Big.
5-2
• Chatterings
will
be absorbed for 24 rnsec.
• Continuous depressions
will
be
accepted first at 24
msec after the depression start, second at 500 msec
after the first, and then at every 150 msec thereafter.
•
All
multiple depressions ·
.shall
be inhibited. Once a
multiple depression
is
made, no key inputs
will
be
accepted until after
all
of
the depressed keys. have
been released.
5-1-4
Key Processings
(1)
[PHONO],
[CD]
Sets the input selector (TC9164N) for either
of
the
input modes keyed in, and makes due indications for
it. Nothing, however, will occur when the depressed
key mode has already been engaged. .
When
either TAPE 1 or TAPE 2 has been keyed on,
the displays for a tape monitored input will be
flashed on and
off
for 10 times at a 1/2 duty and
once every second, to alert the operator
of
the
ongoing tape monitoring.
In
addition, when serial
data
is
being transferred to the analog switch, the
--------------SERVICE
MANUAL
AA·A25/Y
1,
AA·A25L---------------
8
