Kenwood NXR-800H Service Manual

NXR-800H33■ TX_Vocoder DSPIn NXDN mode, the AMBE+2 (TM) vocoder processing isperformed by the IC324 TX_Vocoder_DSP.Audio signal input from the Audio codec IC ADC part(IC309 AINL) terminal is vocoder encode processed andconverted to audio data.CAI data is encoded for correcting errors and convertedto transmitter data.This data is framed, converted to symbol values andmade to pass the base band limitation filter (root nyquistcosine filter and sinc filter). The passed signal turns into amodulating signal. It is output as an analog signal by theAudio codec IC DAC part (IC309 AOUTR terminal).■ Power supply voltage monitoring circuitThis circuit always monitors the external power supplyvoltage assuming that the abnormal power supply voltage isapplied. This circuit consists of X53-413 R67, R68, R71, andR79 and IC7, and X53-414 IC308. If the voltage is reduced,these circuits interrupt the Modem control MPU (IC325) andNXR-800H rapidly shift to the power down state. The IC325A/D converter (pin124) monitors the voltage. It detects thevoltage rises and returns to the normal voltage range.■ Reset circuitReset system diagrams of each device of NXR-800H areattached. With regard to the priority of the reset signal ofeach device, IC303 that prepares the reset signal of IC325has 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 ofIC325.33BU33SH33SHIC700 IC719IC70333SH100K100K100KD16C_RST33SHIC70833MPUIC314IC32550MPUIC3433SH33SH33MPUIC30333MPU33MPU33MPUDSP_RSTRESET_DIC32433MPUIC32350MPUIC3550MPUWPADSP_RSTIC3733SHIC1750MPUEEPROMeachRF unit33SH33SHIC70250MPU33SHfrom RTESYS_RST47K33MPU50MPUWPFig. 26 Reset circuit / 图 26 复位电路CIRCUIT DESCRIPTION / 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-800H 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 -800H 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。