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TK-5400
7. Control Circuit
The control unit has microprocessor IC507, flash
memory IC508, and its peripheral circuits. It controls the TX-
RX unit and transfers data to and from the control unit. The
CPU (IC507) mainly performs the following:
1) Switch between transmission and reception with the PTT
signal input.
2) Read a channel, frequency, and program data from the
memory circuit.
3) Send a frequency program data to the PLL.
4) Control the audio mute circuit by decode data input.
5) Send serial data to output expander (IC701, IC703) to
control various function in the unit.
7-1. CPU
The CPU (IC507) is a 16bit single-chip microprocessor,
equipped with a 64k ROM and 10k RAM. This CPU oper-
ates at 12.288MHz clock and 3.3V DC. Controls the flash
memory IC, the DSP, the receive circuit, the transmitter cir-
cuit, the control circuit, and the display circuit and transfers
data to or from an external device.
7-2. Memory Circuit
IC508 is a flash memory with 8M bits capacity that stores
the transceiver control program for the CPU and the data
such as transceiver channels and operating parameters.
This program can be easily written from an external de-
vices. The data, such as DTMF memories and operating
parameters, are stored into the EEPROM (IC505).
7-3. Shift Register Circuit
IC701 and 703 are interface ICs for the output port expan-
sion. It is used to expand the CPU (IC507) output ports.
IC505
EEPROM
IC506
Reset IC
X501
IC502
TCXO
12.288MHz
Fig. 10 Control circuit
12
CIRCUIT DESCRIPTION
IC508
IC507
FLASH
ROM
IC701,703
Shift
CPU
Register IC
IC605
D/A IC
IC611
IC608
CODEC IC
DSP
IC609
A/D IC
7-4. D/A Converter
IC605 is used as a conventional semi-fixed-resister con-
verter. It controls the followings:
1) Transmission power
2) Modulation level
3) Audio power
4) Frequency
7-5. Key Input
Kl1 or Kl2 becomes HIGH when a key is pressed (or En-
able signal on the optional circuit).
When Kl1 or Kl2 becomes HIGH, Kl0 also becomes HIGH
to trigger the interrupt to IC507 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 routed through Kl1 or Kl2
to the microprocessor. Then, the microprocessor deter-
mines which key is pressed using this signals.
IC2
Q1 Q2 Q3 Q4 Q5
Monitor
Tone1
IC4
SW A
SW B
AND IC
MAN D
Fig. 11 Key input
7-6. Low Battery Warning
The battery voltage is monitored by the microprocessor
(IC507). When the battery voltage falls below the voltage
set by the Low battery warning adjustment, the red LED
blinks to notify the operator that it is time to replace the bat-
tery. If the battery voltage falls even more (approx. 6.0V), a
beep sounds and transmission stops.
Low battery warning
The red LED blinks during
transmission
The red LED blinks and
continuous beep sounds
while the PTT pressed
CLK
CLK
IC504
IC507
DAT
DAT
STB
STB
Level
CPU
Shifter IC
IC5
AND IC
Tone2
OPPTT
KEY1
IC6
AND IC
TCONT
KEY2
Battery condition
The battery voltage is low but
the transceiver is still usable.
The battery voltage is low but
the transceiver is not usable to
make calls.
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