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This function is activated by a low level input to
pin 40 (INH), and during this time, power con-
sumption is held to a level of approximately 10yA.
When the power switch is cut off (placing set in
STANDBY
position), pin 40 goes to a low level,
TC9137P
goes
into
an
inhibit
status,
holding
memory
contents using minimum
current.
Also,
when external power supply is cut (AC line cord
unplugged), the charge stored in backup capacitor
(C184)
protects the contents. stored in memory
for approximately 3 days.
Q44 functions to prevent IC current drain. When
pins 34 and 33 go into an inhibit status
(H level),
the current discharge from these pins can increase
power
consumption.
Q44
is turned
off during
inhibit to prevent this from occurring.
4.6 FREQUENCY DISPLAY CIRCUIT
The synthesizer IC (TC9137P) uses the recep-
tion frequency display static driver IC (TD6301P)
to convert the 5 digit LED numeric display to a
A digit display.
DATA
FREQUENCY
DATA
11 bits
16 bits
1 CYCLE
(1. 8ms)
START
SIGNAL
(400yps )
Fig. 4-7 Frequency data signal
LED
NUMERIC
DISPLAY
2ND
DIGIT
3RD
DIGIT
Awe
mae
wee
4TH
DIGIT
ScD
B
B 3A DP 4G 4F 4E 40 4C 4B 4A
SAF
4
7
EN EIN
MMOMOQOW
During
FM
reception,
the
5th digit displays
either a ''0"' or "5'' (10kHz increments).
The
TC9137P 0/5 terminal (pin 23) is controlled with-
out being passed through TD6301P.
The connec-
tion between TC9137P
and TD6301P
consists of
two timing signal lines and one data signal line.
One cycle of data (Fig. 4-7) is transmitted through
the data line when power is turned on, when tun-
ing frequency
is moved
UP
or DOWN,
during
auto-scan, during memory recall, or when the band
is switched
between
FM/AM.
The
data signal
consists of a 16 bit binary code, with 11 bits of
frequency data and 5 bits of reception band data.
The
11 bits of frequency
data consists
of the
difference
between
the
present
reception
fre-
quency and the lowest frequency obtainable in the
present reception frequency band, in binary-coded
form
(the decimal point and 50kHz
increments
ignored in FM).
:
Using two strings of pulse signals, the TD6301P
converts
the binary coded
serial data into BCD
coded parallel data.
This data is decoded by the
BCD
to 7-segment
decoder
and
output
to the
display.
When switched to the FM
band, TC9137P
pin
23 (0/5) controlling the 5th digit (50kHz incre-
ment display) is held at high impedance when "'0"',
and drops to a low level at '5'.
Q385 and Q34
switch on/off to change the 5th digit of the LED
numberic display between "'0'' and ''5''.
STH
DIGIT
Coa
Fig. 4-8 Frequency display circuit
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