Kenwood TKR-D710 Service Manual page 17

4-2. Memory circuit
The Memory circuit consists of the MCU (IC20), the
SRAM (IC9), and the fl ash memory (IC3).
The fl ash memory has a capacity of 32Mbit that contains
the transceiver control program for the MCU and stores the
data. It also stores the data for transceiver channels and
operating parameters that are written by the FPU. This pro-
gram can be easily written from external devices.
The SRAM has a capacity of 1Mbit that contains work
area and data area.
■ Flash memory
Note: The fl ash memory stores the data that is written by
the FPU, tuning data (Deviation, Squelch, etc.), and fi rmware
program.
■ SRAM (static memory)
Note: The SRAM has a temporary data area and work area.
When the power supply is off, it is backed up by an internal
secondary lithium battery. Therefore, the saved data is not
lost.
4-3. DSP circuit
The DSP circuit consists of a DSP (IC6) and processes
the base band signal. The DSP operates on an external clock
of 18.432MHz (the same as IC20). The I/O section operates
at 3.3V and the core section operates at 1.6V. The DSP car-
ries out the following processes:
■ Digital processing
• 4Level FSK and Baseband fi lter processing
• Vocoder processing between audio codec and modula-
tion/demodulation
• CAI processing, such as error correction encoding/decod-
ing and interleaving
• AFC loop control
• Frame synchronization and Time tracking
• Data scrambling
■ Analog FM processing
• Pre-emphasis/De-emphasis
• QT/DQT encoding/decoding
• DTMF encoding/decoding
• Compressor/Expander processing
• Voice scrambler processing
■ Audio or Modulation function
• Transmit/Receive audio fi ltering processing
• Microphone amplifi er AGC processing
• Audio soft mute processing
• Modulation level processing
• Squelch Filtering
■ Other function
• Courtesy tone
• Repeater operating
• Analog/Digital Mixed mode
CIRCUIT DESCRIPTION
4-4. Squelch circuit
nal from IC6 after fi ltering through the BPF circuit. The pro-
cessed digital noise signal is applied to CODEC IC14, and is
converted from digital to analog. The amplifi ed signal is then
converted to a DC signal by the detection circuit. The con-
verted signal is fed back to IC20.
FLASH
33BU
SRAM
33M 16M
4-5. Power supply circuit
IC304, IC305 and IC306.
This 13.6V voltage is supplied from TX-RX unit (X57-894).
to 5.0V. IC303, IC304, IC305 and IC306 are connected to
IC301. IC303 and IC306 are 3.3V voltage regulators. IC304
is a 1.5V regulator IC, and IC305 is a 1.6V regulator IC.
lithium battery is used to back up the SRAM and RTC data
when no external DC power source is available.
The Squelch circuit amplifi es the demodulated noise sig-
33M
/FRST
IC3
A[0~21], D[0~15],
/RD, /WR, /CS0, /WP
A[0~17], D[0~7],
IC9 /RD, /WR, /CS2
A[0~20], D[0~15], /RD,
/WR, /HRDY, /CS3, /HDS2
/DRST
/MCCSXCN, /MCCSRCN, MCDICN,
MCDOCN, MCSCKCN
MCSCKAF, /MCCSAF, MCDIAF, MCDOAF
DSP
/SYMTIM, /DINT, /DWUP, FSDET, /HINT
IC6
/PCS_DSP
MAIN_CLK
Buffer
IC16
VREF
/PDN,
Squelch
LRCLK,
DAC
SDTI,
IC14
BICLK
IC13(A/2,B/2)
Fig. 14 Control circuit
The X53-458 circuit consists of IC301, IC302, IC303,
IC301 is a DC/DC converter that converts 13.6V to 6.0V.
IC302 is connected to IC301 and regulates the voltage
CN302 is the connector for the lithium battery. The
TKR-D710
33M 15M 33A
/FRST
MCU
IC20
/DRST
VCTCXO
X1 BSHIFT
(18.432MHz)
XTAL_IN
ADC1
LDR
AMP AMP AMP
Q4 IC15(A/2)
17