Kenwood TK-7302 Service Manual page 13

5-1. Memory Circuit
The transceiver has a 256k-bit EEPROM (IC703). The EE-
PROM contains adjustment data. The MCU (IC702) controls
the EEPROM through three serial data lines.
EEPCK
EEPDI
IC702
MCU
EEPWP
Fig. 11 Memory circuit
5-2. Display Circuit
The MCU (IC702) controls the 7-segment LED Display
and LEDs.
When power is on, the MCU will use the MBL line to
control the key backlight LEDs.
When the transceiver is busy, the GLED line goes high,
Q1 turns on and the green LED (D23) lights after Q4 turns
on. In transmit mode, the RLED line goes high, Q2 and Q8
turn on and the red LED (D23) lights.
BLED will be set high when the function select (FPU set-
ting) is on, Q6 turns on and the blue LED (D22) lights.
The dimmer function is controlled by the switch (Q5).
The LED driver (IC1) controls the functions of the 7-segment
LED through the LEDI, LECE, LECL, LELH lines from the
MCU.
LEDM
Q5
SW
LEDI
LECE
IC1
LECL
LED
driver
LELH
MBL
Q3
SW
IC702
MCU
GLED
Q1
SW
RLED
Q2
SW
BLED
Fig. 12 Display circuit
5-3. Key Matrix Circuit
The TK-7302 front panel has function keys. Each of them
is connected to a cross point of a matrix of the KMI1 to
KMO3 ports of the MCU. The KMO1 to KMO3 ports are al-
ways high, while the KMI1 to KMI3 ports are always low.
The MCU monitors the status of the KMI1 to KMO3
ports. If the state of one of the ports changes, the MCU as-
sumes that the key at the matrix point corresponding to that
port has been pressed.
CIRCUIT DESCRIPTION
IC703
EEPROM
Display
7-segment
D1~D5
Key backlight
Q4
SW
D23
Q7
SW
Q8
SW
D22
Q6
SW
TK-7302/7302
KMO1
CH UP
KMO2
IC702 VOL DN
KMO3
MCU
KMI3
KMI2
KMI1
Fig. 13 Key matrix circuit
6. Signaling Circuit
6-1. Encode
■ Low-speed data (QT, DQT)
Low-speed data is output from pin 1 (LSDO) of the MCU
(IC702). The signal passes through a low-pass CR fi lter. The
signal is mixed with the audio signal and goes to the VCO
and TCXO (X1) modulation input after signal processing in
the baseband IC (IC701).
■ High-speed data (2-tone)
High-speed data (HSD) is output from pin 2 (HSDO) of
the MCU.
The signal passes through a low-pass CR fi lter. TX devia-
tion making an adjustment by MCU is applied to the base-
band IC (IC701). The signal is mixed with the audio signal
and goes to the VCO and TCXO.
The RX tone is audio output of baseband IC (IC701) at
the same time to audio power amplifier and then to the
speaker.
LSDO
IC701
QT/DQT Baseband IC
IC702
MCU
DTMF/
HSDO
MSK
2-TONE
Fig. 14 Encode
■ MSK / DTMF
MSK and DTMF signal is self generated by the baseband
IC (IC701).
The TX deviation adjustment is done by the output gain
of the baseband IC (IC701), and is routed to the VCO. When
encoding MSK/DTMF, the microphone-input signal is muted.
6-2. Decode
■ Low-speed data (QT, DQT)
The demodulated signal from the FM IC (IC500) will input
to the baseband IC (IC701) to remove frequencies of 300Hz
or more.
The signal is input to pin 88 (LSDI) of the MCU. The
MCU digitizes this signal, performs processing such as DC
restoration, and decodes the signal.
V /7302H/7302H
( )
B A S
r
C
VOL UP CH DN
TCXO
MOD
X1 IC1
TCXO PLL
VCO
MOD
VCO
V
( )
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