Kenwood TK-5210G Service Manual page 23

6-2. Memory Circuit
Memory circuit consists of the ASIC (IC10) and the
SRAM (IC4), the fl ash memory (IC1). The fl ash memory has
capacity of 32M-bit that contains the transceiver control
program for the ASIC and stores the data. It also stores the
data for transceiver channels and operating parameter that
are written by the FPU. This program can be easily written
from external devices. The SRAM has capacity of 1M-bit
that contains work area and data area.
■ Flash memory
Note: The flash memory stores the data that is written
by the FPU (KPG-95DG), tuning data (Deviation, Squelch,
etc.), and fi rmware program (User mode, Test mode, Tuning
mode, etc.). This data must be rewritten when replacing the
fl ash memory.
■ SRAM (static memory)
Note: The SRAM has temporary data area and work area.
When the power supply is off, it is backed up by an internal
secondary lithium battery. Therefore, the save data does not
break.
■ Real-time clock
The clock function is based on real-time clock IC (IC7).
When the power supply is off, it is backed up by an internal
secondary lithium battery
6-3. LCD
The LCD is controlled using the bus lines on the connec-
tor (CN1) of the control unit. The LCD contrast voltage is
corrected using IC712.
6-4. Temperature Detection Circuit
The temperature detection circuit detects the tempera-
ture using a temperature IC (IC714) and corrects the thermal
characteristic change of the squelch or LCD.
6-5. Key Detection Circuit
Keys are detected using Key scan circuit in IC10.
The /KEYI* signals that are normally pulled down go high
when any key is pressed.
6-6. Low Battery Warning
The battery voltage is divided using R712 and R714 and
is detected by the ASIC (IC10). When the battery voltage
falls below the voltage set by the Low battery warning ad-
justment, the red LED blinks to notify the operator that it is
time to replace the battery. If the battery voltage falls even
more (approx. 5.8V), a beep sounds and transmission stops.
Low battery warning
The red LED blinks during
transmission.
The red LED blinks and the
warning tone beeps while the
PTT switch is pressed.
CIRCUIT DESCRIPTION
Battery condition
The battery voltage is low but
the transceiver is still usable.
The battery voltage is low and
the transceiver is not usable to
make calls.
TK-5210
6-7. Battery Type Detection
The transceiver automatically detects the battery type,
measuring the resistance between the S-terminal and GND
terminal on the battery pack and changes the supplied volt-
age to the S-terminal as below. The ASIC (IC10) then de-
tects the battery type.
Battery type Input voltage of S-termial
Battery case 0~0.2V
Li-ion battery 0.85~1.02V
Ni-Cd battery 3.23~3.37V
Ni-MH battery 1.71~1.95V
6-8. VOX
The VOX function can be used only with an external mi-
crophone.
The VOX (Voice Operated Transmission) function detects
voice input to the microphone and automatically switches
between transmission and reception. However, if a scram-
bler board is installed (Extended Function Voice Scrambler is
selected with FPU), VOX does not operate.
If the microphone input exceeds a certain level, transmis-
sion automatically begins. If the input falls below a certain
level, the transceiver automatically returns to receive mode.
The transceiver realizes this function using DSP (IC8).
6-9. DSP
The DSP circuit consists of a DSP (IC3) and processes
the base band signal. The DSP operates on an external clock
of 18.432MHz (the same as the X2), the I/O section oper-
ates at 3.3V and the core section operates at 1.5V. The DSP
carries out the following processes:
• C4FM
• Analog FM pre-emphasis/de-emphasis
• Vocoder processing between audio codec and modula-
tion/demodulation
• CAI processing, such as error correction encoding
• QT/DQT encoding/decoding
• DTMF encoding/decoding
• MSK encoding/decoding
• 2-tone encoding/encoding
• Compressor/expander processing
• Transmit/receive audio fi ltering processing
• Microphone amplifi er AGC processing
• Audio mute processing
• Modulation level processing
( G )
Resistor value
Short
47kΩ
Open
150kΩ
23