User's Manual
CIRCUIT DESCRIPTION
6.
Control unit
The control unit colisists of CPU )IC2091 and its
peripheral circuits. It controls the TX and RX units and
transfers data to and from the LCD assembly. The
CPU has the foow~ng main
functions:
1)
Switchlrig betweeri transmission and reception
according to the
PT slgnal input.
D/A
converter
IC6 is used as a conventonal semi-fixed-resistor
converter It sets the
following:
1) Reference oscillator frequency
2) Transmission power
3) Modulation level
4) Audio power
2)
Head~ng system, group, frequency, and program
6-2.
TX
encode data
data frorn the mernory circuit.
3) Sending frequency data to the PLL.
The CPU (IC209) transmits encode data.
4) Turning the squelch on and off according to the
pulse signal input from the squelch circuit.
QT, DQT,
LTR
5) Controlling the audio mute circ~iit according to
These data items are output from CPU pin 33. The
signal from this pin passes through the CR low-pass
input decode data.
filter and goes to the
summing amplifier (IC212) in the
6) Sending encode data
microphone amplifier. It is
mixed with the audio signal
7)
Sendlng data to the D/A converter.
and output to the splatter filter. It then goes to the
D/A
6-1.
Memory circuit
converter (IC6) and on to the VCXO and VCO.
IC201 is a 2-Kbit EEPROM that stores adjustment
6-3.
RX
decode
data
and backup data. IC207 is a 256-Kbit flash memory
that contains the transceiver control program, and
Low-speed data
(QT, DQT, LTRI
The receive detection signal is amplified by IC2 (21
channel
and
Operating
feature
data
The
and
21, and passes through a ow-pass filter lC204 (112) to
data can be easily wrltten into the memory froln
remove audio components. This signal is input to pin
external equipment.
IC208 and IC210 control the
27
of
the
CpU,
writing of data into IC207.
The CPU digitizes this signal, performs processing
such as DC restoration, and decodes the signal.
Shift register
IC10 is an interface IC for I/O port expansion.
It
IS
used to expand the CPU (IC209) output ports.
IC207
IC6
1c2
(212)
Fig.
7
Control
unit
block diagram