Technics ST-9038 User Manual

*
t
ESIZER
1-5 Programmablefrequencydivider
The
prograr"nmable
frequency
(variable)
divider
plays
the
most important
role in
setting the
frequency
for the PLL
synthesizer.
Thefrequencydividingratio
1ln=1/983(9BB)
-
llBOnecessaryfortherespectivecountryisdone
in this
section. ln
the case
of this equipment,
lC's
SVlSN74LS192
and
¡rPDB61
are series-con-
nected, and the results of division
by the fixed
and variable
codes are totalled to achieve
the
dividing
ratio.
"1"
74L574
ü
o
$
fin
,Ç
.O
-.9
87
(88)
-
107
To
Phase
comparator
Programmable
frequency
divider circuit
1-5-1 Operational description
of
lC
SVISN74LS192
4-bit BCD
up/down
programmable
counter.
ln this circuit,
it is used
as
a down
counter, and the
borrow output is fed into
¡rPDB61C.
When the BCD
output changes
from
0 to
g,
a down counter
input
pulse
of
negãtive
polarity
äppears
at
the
borrow output.
Also,
when the
load
line is
ar
"1"
level, the inputs
of tl-ie
preset
inputs
Da
-
Do are inhibited
and
the counter
counts
down the
frequency.
But
when
the
load
signal becomes
"0"
level,
the
preset
data
are
given priority
and
set ¡nto
each
F/F
irrespective
of
the input frequency conditions.
When
the
load line
is again
shifted
back
Io
"1"
level,
the
counter counts down from the
preset
value.
c
o
õ
D
ocK
CLR
B
74L574
oA oB oc oD
74L5192
Load
Db Dc Dd
down
Ða
Borrow
CLR
P2
P3 P4 P5
P6
P7 P8
pPD861C
OUTln
3

Technics ST-9038 Specifications

General

Brand	Technics
Model	ST-9038
Category	Tuner
Language	English