Kenwood NXR-700 Service Manual page 20

NXR-700
electronic volume IC8.
On the other hand, the transmitting audio signal output
from IC3 is amplifi ed by IC9 (A/4), applied to pin 3 (AINL) of
CODEC IC4, and is then converted from analog to digital at
a sampling frequency of 16.128kHz. The digitized transmit-
ting audio signal is AGC-processed, pre-emphasized and
fi ltered, except for the 300Hz to 3kHz range, by DSP IC37,
■ Shift register circuit
The MPU (IC34) transmits serial data to shift registers
IC923 from IC923 to IC960 and from IC960 to IC963 in the
display circuit (X56-311 B/3, C/3).
Additionally, it transmit serial data to the control unit (X53-
413) IC1 and IC22 and the transmitter unit (X56-311) IC703.
This serial data can control various functions of each unit.
■ Power supply circuit
This circuit consists of X53-413 IC6, IC10, IC11, IC15,
IC16 and 18, and X53-414 IC305, IC306, IC307 and IC329.
IC11 is a DC/DC converter that converts 13.2V to 5.0V.
IC10 is a DC/DC converter that converts 13.2V to 8.0V. IC16
is the 5.0V AVR and connected to IC10. IC6, IC15, IC305
and IC329 is the 3.3V AVR. IC18 is the 1.8V AVR. IC306 is
the 1.5V AVR. IC18 and IC306 is connected to IC329.
■ Flash memory (RF control MPU)
IC17 is an 8M bit Flash memory and contains MPU fi rm-
ware for controlling the RF.
■ EEPROMs circuit
The EEPROM is a built in receiver unit (X55-309), trans-
mitter unit (X56-311) and Final unit (X45-385).
The RF control MPU controls these EEPROMs by the IIC
bus.
20
CIRCUIT DESCRIPTION
RX detected signal
(AINR)
RD
TX modulation signal
Local Mic
(AINL)
TA
[Frequency response]
REPEAT
Fig. 24 An audio signal course and the frequency characteristic
and is then feed back to CODEC IC4, converted from digital
to analog, and the analog signal is output from pin 15 (AOU-
TL). The transmitting signal from the AOUTL is amplifi ed by
IC9 (B/4), passed through the IC9 (C/4) low-pass fi lter, and
sent to the IC9 (D/4) summing amplifi er.
IC31 is a counter IC. The clock required for the CODEC
and DSP is generated by dividing the 16.515072MHz clock
signal supplied by the DSP IC37.
CODEC IC
IC4: AK4550VTP
2
16
RX
(AOUTR)
REPEAT
3
15
TX
(AOUTL)
TD
300Hz 3kHz
RX (De-emphasis)
TX (Pre-emphasis)
(300Hz~3kHz Flat)
6-2. X53-414
■ Main MPU
The Main MPU (IC703) is a 32-bit RISC microprocessor
incorporating a 16 kilobytes cache memory.
The main MPU controls the Flash memory, SDRAM,
SRAM, LAN IC, RS-232C driver, receiver and real-time clock
(RTC) IC besides RF control MPU and UART communica-
tion with modem control MPU.
■ LAN interface
NXR-700 is equipped with a 100Base-TX or 10Base-
T LAN interface. This circuit consists of IC719, IC720 and
J700. IC719 is a control IC. IC720 is a EEPROM, and
saves the MAC address.
■ Real time clock (RTC) circuit
This circuit consists of IC710 and X701. IC710 is a Real
Time Clock. X701 is a crystal oscillator. IC710 is connected
to IC703 (Main_MPU) via the IIC bus. The oscillating fre-
quency of X701 is 32.768kHz. It is backed up by a recharge-
able lithium battery (BA300). The IC710 clock data is used
after resetting the backup.
■ RS-232C circuit
NXR-700 is equipped with a RS-232C interface. It is
connected to a PC with pin 9 female RS-232C cross-wired
cable. It uses the FPU and writes the fi rmware. IC705 is a
RS-232C driver receiver IC, and interfaces at the TTL level.
RA
RX audio amp.
TX VCO
(Modulation circuit)