Kenwood NXR-700H Service Manual page 33

■ TX_Vocoder DSP
In NXDN mode, the AMBE+2 (TM) vocoder processing is
performed by the IC324 TX_Vocoder_DSP.
Audio signal input from the Audio codec IC ADC part
(IC309 AINL) terminal is vocoder encode processed and
converted to audio data.
CAI data is encoded for correcting errors and converted
to transmitter data.
This data is framed, converted to symbol values and
made to pass the base band limitation filter (root nyquist
cosine fi lter and sinc fi lter). The passed signal turns into a
modulating signal. It is output as an analog signal by the
Audio codec IC DAC part (IC309 AOUTR terminal).
■ Power supply voltage monitoring circuit
This circuit always monitors the external power supply
voltage assuming that the abnormal power supply voltage is
applied. This circuit consists of X53-413 R67, R68, R71, and
R79 and IC7, and X53-414 IC308. If the voltage is reduced,
these circuits interrupt the Modem control MPU (IC325) and
NXR-700H rapidly shift to the power down state. The IC325
A/D converter (pin124) monitors the voltage. It detects the
voltage rises and returns to the normal voltage range.
■ Reset circuit
Reset system diagrams of each device of NXR-700H are
attached. With regard to the priority of the reset signal of
each device, IC303 that prepares the reset signal of IC325
has the highest priority. Software of IC325 can activate de-
vices including IC323, IC324, IC703, IC700, IC702, IC719,
IC34, and IC17. Software of IC703 can activate the reset of
IC325.
33MPU
33MPU 33MPU
IC303
RESET_D
33MPU
CIRCUIT DESCRIPTION /
33SH
D16C_RST
33SH 33SH
IC703
33SH
IC708
SYS_RST
33MPU
IC325
IC314
33MPU 33MPU
IC324 IC323
DSP_RST
Fig. 26 Reset circuit / 图 26 复位电路
电路说明
■ TX_ 声码器 DSP
在 NXDN 模式中，由 IC324 TX 声码器 DSP 进行 AMBE+2(TM)
声码器处理。
从 IC ADC 部分 (IC309 AINL) 端子输入的音频信号经过声
码器编码处理后，转换成音频数据。
CAI 经过纠错编码后转换成发射机数据。
该数据成帧、转换为符号值并通过基带限制滤波器 ( 根奈
奎斯特余弦滤波器和 s i n c 滤波器 )。通过的信号变成调制信
号。它被音频编解码器 IC 的 DAC 部分 (IC309 AOUTR 端子 )
作为模拟信号输出。
■电源电压监测电路
该电路始终在假定施加异常电源的情况下监测外部电源的
电压。该电路由 X53-413 R67、R68、R71、R79、I C7 和 X53-
414 IC308 组成。如果电压下降，这些电路会中断调制解调器
控制 MPU(IC325)，NXR-700H 迅速转换到掉电状态。IC325 A/
D 转换器 ( 针脚 124) 监测电压。它检测电压的升高并返回正
常电压范围。
■复位电路
附有 N X R -700H 各装置的复位系统图。在各装置的复位信
号的优先顺序方面，准备 I C325 的复位信号的 I C303 具有最
高优先权。I C325 的软件可激活包括 I C323、I C324、I C703、
I C700、I C702、I C719、I C34 和 I C17 在内的装置。I C703 可
启动 IC325 的复位。
33BU
33SH
IC700
50MPU
from RTE
50MPU
WP
33SH
50MPU
WP
IC17
NXR-700H
33SH 33SH
IC719 IC702
50MPU 33SH
IC34
50MPU
IC35
50MPU 33SH
EEPROM
each IC37
RF unit
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