Kenwood TKR-850 Service Manual page 22

TKR-850
5. Control Circuit
The control circuit mainly located in the control section of
TX-RX unit (X57-627 B/2) consists of the following : 5-1 CPU,
5-2 memory circuit, 5-3 CPU clock shift, 5-4 shift register
circuit, 5-5 display circuit, 5-6 DSP circuit, 5-7 base-band cir-
cuit, 5-8 RS-232C circuit, and 5-9 power supply circuit.
5-1. CPU
The CPU (IC604) is a 16bit single-chip microcomputer
containing a 32k ROM and 3k RAM. This CPU controls the
flash ROM, the DSP, the receiver circuit, the transmitter cir-
cuit, 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 pro-
cessing program for DSP and data such as channels and op-
erating 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 (X57-627). 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
located in display unit, IC602, IC623, IC7 located in TX-RX
unit) from the CPU (IC604) to control various functions in the
unit.
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CIRCUIT DESCRIPTION
Display unit (X54-333-20 A/2)
CLK,SOE, CLK,SOE,
STB1 STB1
SI SI
SO
Shift Reg. 1 Shift Reg. 2
BU4094BCFV BU4094BCFV
SW
SW
KEY LAMP
1~6
Fig. 8 Display circuit
5-5. Display Circuit
The display circuit (X54-333) contains two 7-segment
LEDs D506, D507 (orange : see the operation manual for
details of display), D503 (red : transmission), D504 (green :
busy), 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
SW
Q600
BEAT
SHIFT
IC603/606 INTERFACE IC
IC618
X601
16.515
MHz
SW
Q600
IC614
BEAT
CODEC IC
SHIFT
Fig. 7 Control circuit
PF1~6
KEY1~5
CLK,SOE, CLK,SOE,
STB1 STB1
SI
SO SO
Shift Reg. 3 Shift Reg. 4
BU4094BCFV BU4094BCFV
SW
SW SW
TX BUSY
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