Control Circuit; Cpu; Memory Circuit; Display Circuit - Kenwood TKR-750 Service Manual

5. Control Circuit

The control circuit mainly located in the control section of
TX-RX unit (X57-695 B/2) consists of the following : 5-1 CPU,
5-2 memory circuit, 5-3 CPU clock shift, 5-4 shift register cir-
cuit, 5-5 display circuit, 5-6 DSP circuit, 5-7 base-band circuit,
5-8 RS-232C circuit, 5-9 power supply circuit, and 5-10 5-tone
decode circuit.

5-1. CPU

The CPU (IC604) is a 16bit single-chip microcomputer con-
taining a 32k ROM and 3k RAM. This CPU controls the flash
ROM, the DSP, the receiver circuit, the transmitter circuit,
the control circuit, and the display circuit and transfers data to
or from an external device.

5-2. Memory Circuit

IC609 has a flash ROM with a capacity of 2M bits that
contains the control program for the CPU, the signal process-
ing program for DSP and data such as channels and operating
features.
This program can be easily written from an external de-
vice. Data such as the operating status are programmed into
the EEPROM (IC600).
5-3. CPU Clock Shift
There are the 14.754MHz clock for the CPU (IC604) and
the 16.515MHz clock for the DSP (IC618) at the control sec-
tion of TX-RX unit (X57-695). When these clocks are multi-
plexed with the reception frequency, they become an inter-
nal beat signal. To prevent this, by tuning Q600 and Q604 on
the clock frequency is shifted. (Shift on/off can be set
through programming.)
5-4. Shift Register Circuit
Serial data is sent to the shift register (IC502 to IC505 lo-
cated in display unit, IC602, IC623, IC7 located in TX-RX unit)
from the CPU (IC604) to control various functions in the unit.
CIRCUIT DESCRIPTION
Display unit (X54-3330-21 A/2)
CLK,SOE, CLK,SOE,
STB1 STB1
SI SO SI
Shift Reg. 1 Shift Reg. 2
BU4094BCFV
BU4094BCFV
SW
SW
KEY LAMP
1~6
Fig. 9 Display circuit

5-5. Display Circuit

The display circuit (X54-333) contains two 7-segment
LEDs D506, D507 (orange), D503 (red : transmission), two-
color D504 (green : busy, orange : selective called), two-color
LED D505 (red : backup, green : main DC), LEDs in switches
S501 to S506, IC502, IC503, IC504, and IC505 to display this
model channels and states.
IC502 to IC505 are shift registers which convert serial data
from the CPU to parallel data and light LEDs.
Q507, Q510, and Q511 are switching transistors which
control two-color LED D505.
IC506, and IC507 are three-pin power supply ICs which
produce power used for the display circuit.
TX-RX unit (X57 B/2): CONTROL
IC600
EEPROM
IC601
Reset IC
X600
14.754
MHz
Q600 SW
BEAT
SHIFT
IC603/606 INTERFACE IC
IC618
X601
16.515
MHz
Q600 SW
IC614
BEAT
CODEC IC
SHIFT
Fig. 8 Control circuit
PF1~6
KEY1~5
CLK,SOE, CLK,SOE,
STB1 STB1
SO SI SO
Shift Reg. 3
Shift Reg. 4
BU4094BCFV
BU4094BCFV
SW
SW SW SW
TX CALL BUSY
TKR-750
IC604
IC609
FLASH ROM
IC620
232C DRIVER
CPU
IC615
D/A IC
IC602/623
Shift Register IC
DSP
IC613
DIVIDER
DAT
SW
Main DC/
BACKUP
15