Kenwood TK-190 Service Manual page 16

TK-190
7. Control Circuit
The control unit circuit consists of microprocessor IC406
and flash memory IC414. It controls the TX-RX unit and
transfers data to and from the control unit. The CPU (IC406)
mainly performs the following :
1) Switching between transmission and reception by PTT
signal input.
2) Reading channel, frequency, and program data from the
memory circuit.
3) Sending frequency program data to the PLL.
4) Controlling squelch on/off from the squelch circuit.
5) Controlling the audio mute circuit by decode data input.
6) Transmitting encode data (QT, DQT).
7) Sending serial data to output expander (IC400, IC403,
IC404 and IC405) to various function in the unit.
7-1. Memory circuit
IC414 has a flash memory with a capacity of 2M bits that
contains the transceiver control program for the CPU and
data such as transceiver channels and operating features.
This program can be easily written from an external de-
vices. Data, such as DTMF memories and operating status,
are programmed into the EEPROM (IC412).
IC406
CPU
Fig. 9 Memory circuit
7-2. CPU clock
The CPU clock is generated by VCXO (16.8MHz) and it is
fed through an inverter, IC416. This clock was divided into a
half cycle (1/2 frequency) at the internal CPU. The CPU fur-
ther divides this clock to utilize it as the various clocks.
IC406
x1
IC416 (3/3)
CPU
x2
Fig. 10 CPU clock circuit
7-3. Shift register
IC400, 403, 404 and 405 is an interface IC for output port
expansion. It is used to expand the CPU (IC406) output
ports.
16
CIRCUIT DESCRIPTION
IC412
EEPROM
IC415
ADDRESS
DECODE
IC414
FLASH
ROM
IC416 (1/3)
INV VCXO
INV
to PLL
7-4. D/A converter
IC1 and IC603 is used as a conventional semi-fixed-resis-
tor converter. It sets the following :
1) RX filter tuning
2) Transmission power tuning
3) Modulation level tuning
4) Audio power tuning
7-5. Key input
KI1 or KI2 becomes HIGH when any key is pressed (or
Enable signal on the optional circuit).
When KI1 or KI2 becomes HIGH, KI0 also becomes HIGH
to trigger the interrupt to IC406 in order to start the key
scan.
When the key scan starts, the output terminals (Q1-Q5)
become LOW. Only the key sensing circuit remains HIGH.
When a key is pressed, the signal is routed through KI1 or
KI2 to the microprocessor. Then, the microprocessor deter-
mines which key is pressed using this signals.
IC2
Q1 Q2 Q3 Q4 Q5
Monitor
SW A
X1
CLK,DAT,STB
Tone1 Tone2 OPPTT
OPPTT
IC4
SW B TC7SH08
TCONT
FU
MAND TCONT
Fig. 11 Key input
IC406
CPU
KEY1
KEY2