Kenwood TK-7100 Service Manual page 20

TK-7100
Control Circuit
The CPU carries out the following tasks:
1) Controls the WIDE, NARROW, TX/RX outputs.
2) Adjusts the AF signal level of the AF filter (IC251) and
turns the filter select compounder on or off.
3) Controls the display unit.
4) Controls the PLL (IC401).
5) Controls the D/A converter (IC161) and adjusts the vol-
ume, modulation and transmission power.
IC101
CPU
Fig. 10 Control circuit
■ Memory Circuit
The transceiver has a 64k-bit EEPROM (IC66). The
EEPROM contains adjustment data. The CPU (IC101) con-
trols the EEPROM through three serial data lines.
IC101
CPU
Fig. 11 Memory circuit
■ Display Circuit
The CPU (IC101) controls the display LCD and LEDs.
When power is on, the CPU will use the MBL line to control
the LCD illumination and key backlight LEDs.
The dimmer function is controlled by the switch Q11. The
LCD controller (IC2) controls the functions of the LCD
through the CE, CK, DI lines from the CPU.
CE
CK
IC101
DI
CPU
MBL
Q6
SW
Fig. 12 Display circuit
20
CIRCUIT DESCRIPTION
CK
IC161
DT
D/A
LD
converter
IC401
PLL
PLLE
EEPCK
EEPDT
IC66
EEPROM
EEPWP
COM0~
COM3
IC2
LCD
SEG0~
LCD
SEG30
controller
DIM
Q10
SW
D2~D5
Q9
SW
D19~D26,
D28~D31
Q11
SW
■ Key Matrix Circuit
The TK-7100 front panel has function keys. Each of them
is connected to a cross point of a matrix of the KMI1 to KMO2
ports of the microprocessor. The KMO1 to KMO2 ports are
always high, while the KMI1 to KMI4 ports are always low.
The microprocessor monitors the status of the KMI1 to
KMO2 ports. If the state of one of the ports changes, the
microprocessor assumes that the key at the matrix point cor-
responding to that port has been pressed.
KMI1
KMI2
KMI3
IC101
KMI4
CPU
KMO2
KMO1
Fig. 13 Key matrix circuit
■ Encode
The QT and DQT signals are output from QT/DQT of the
CPU (IC101) and summed with the external pin DI line by the
summing amplifier (IC203) and the resulting signal goes to
the D/A converter (IC161). The DTMF signal is output from
DTMF of the CPU and goes to the D/A converter (IC161). The
signal is summed with a MIC signal by the summing amplifier
(IC203), and the resulting signal goes to the D/A converter
(IC161).
The D/A converter (IC161) adjusts the MO level and the
balance between the MO and QT/DQT levels. Part of a QT/
DQT signal is summed with MO and the resulting signal goes
to the VCOMOD pin of the VCO. This signal is applied to a
varicap diode in the VCO for direct FM modulation.
IC203
QT/DQT
SUM
AMP
IC101
DI
CPU
IC203
DTMF
IC161
SUM
D/A
AMP
Fig. 14 Encode
VOL
MON
UP
VOL
SCN
DN
CH
UP
CH
DN
TCXO
MOD
X401 IC401
TCXO PLL
IC161
VCO
D/A
VCO
MOD
HT