Programmable Frequency Divider; Frequency Division In Fixed Code Pressetting - Technics ST-9038 Manual

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ö
PLL
SYNTHESIZER
This
PLL lC
is designed
for
CB
and has various functions, which include the following components.
(1
)
Programmable frequency
divider
Changing
the
level
of terminal
@
V to "O" (l-
level) causes P1
-
PB
to
be
directly
connected
to the
program terminals
of the programmable
divider.
Then
the
programming is performed in
accordance
with the
binary
codes
and frequency
dividing can
be done up
to
3
-
255.
P1
-
P6 are used
in this equipment, but
P7
and
PB are
not
used
Also, P6 is fixed at
"1",
and
the
codes added
to Pl
-
Pb make the frequency divíding ratio
variab
le.
(2)
Reference frequency
oscillator and its frequency divider.
Connecting
a
crystal oscillator element
to
X1
-
X2
makes higher precision frequencies
obtainable. ln
this
case
a
12.5 KHz crystaloscillator element
is
connected, and the frequency
is divided by the divider with
a
stage
of
FIF
and
9 bits, thus obtaining the
reference
frequency
as
the
comparison frequency
of the
PLL.
(3)
Phase
comparator
The
reference
frequency 12.5 KHz obtained in (2)
is
compared
with the
12.5
K{zobtained
by
division
of
the
Vco, and the difference
in
phase between these
two,
if
any,
appears
at
the
output of the
phase comparator.
il^
1-5-2
Frequency division in fixed code presetting
fín
Contents
of
74L5192
9-1
9-2
5
Borrow.out of
7
4L5192
t
o
I
(o)
I
9
o
$
Contents of
lPD861C
Output
of
,¡ PD861c
A
74L574
-O
B.
74L574
D
B
74L574 A
o
57
56
t
(
Load
signal)
5