Pioneer F-7 Series Service Manual page 9

MULlIVIBRÂlOR
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Fig. 4-5 Memory store/call circuit
FM (AM)
band, indicator continues to flash.
Memory recall is by designating one of the
Smory
address pins between 14 and 1g (NI-l-
M6). This applies a low level input to the
causing the broadcast frequency stored in
memory to be tuned to and illuminates the corres-
ponding indicator.
lilhen the band is switched between FM and AM,
a signal from the band switch detection circuit
causes Q28 to momentarily eome on, and tuning
automatically
goes to the frequency stored in
memory 1 (STATION 1).
Memory Hold
The power switch (ON/STANDBy) for the F-7
is located in the second stage of the power trans_
formers (Fig. a-6). Power continues to be supplied
to TC9137P even after the porver switch is tumed
off (in STANDBY position).
TC9137P ha.s a selfcontained inhibit function
allowing it to set all its functions to a static
condition (oscillations stopped, all inputs locked,
indicator drives tumed off, all outputs set to L
Ievel).
This function is activated by a low level
input to pin 40 (IÎi-H), and during this time, polver
consumption is held to a level of approximately
10pA. When the power switch is eut 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 exùemal power supply is cut (AC line cord
unpluged), the charge stored in backup capacitor
(C210) protects the contents stored in memory
for approximately 3 days.
Q39 functions to prevent IC current drain. When
pins 33 and 34 go into an inhibit status (H level),
the cunent discharge from these pins can increase
power consumption.
Q39 is turned off during
inhibit to prevent this from occurring.
4.6 FREOUENCY DISPLAY CIRCUIT
The synthesizer IC(TC913?P)
uses the re-
ception
frequency
display static
driver
IC
(TD6301P) to convert the b digit LED numeric
display to a 4 digit display.
During FM reception, the bth digit displays
either a "0" or "5" (10kHz increments). The TC
9137P 0/5 terminal (pin 28) is controlled without
being passed through TD6g01p.
The connection
between TC9137P and TDGBO1p 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 tuning
frequency is moved Up or DOWN, during auto_
scan, during memory recall, or when the band is
switched between FM/AM.
The data signal con-
sists 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 frequen_
cy and the lowest frequency obtainable in the
present reception frequency band, in binary-coded
form (the decimal point and bOkHz incremenb
ignored in FM).
Using two strings of pulse signals, the TD6B01p
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 dis_
play.
I
ASTAALS
I
pin
that
Fig. 4-6 Memory backup circuit