Kenwood NXR-700 Service Manual

Also see for NEXEDGE NXR-700: Brochure Instruction manual Service manual Instruction manual Instruction manual

Contents

NXR-70022■ 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 baseband 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-700 rapidly shift to the power down state. The IC325A/D converter (pin 124) monitors the voltage. It detects thevoltage rises and returns to the normal voltage range.■ Reset circuitReset system diagrams of each device of NXR-700 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.■ Clock shift circuitNXR-700 control unit has a crystal oscillation circuitshown below.X53-4132-71:14.7456MHz (IC34 and X1)16.515072MHz (IC37 and X2)X53-4140-10:14.7456MHz (IC325 and X301)25.8048MHz (IC37 and X2)25MHz (IC719 and X702)Each oscillation circuit turns on the NPN transistor“2SC4738(GR)F” and staggers the oscillating frequencyby approximately –70ppm. This may prevent interferenceagainst transmitter and receiver frequencies. Each transistoris turned on and off by the FPU.■ Flash memory (Main MPU)IC702 is a 128M bit Flash memory and contains the firm-ware of the Main MPU.■ Flash memory (Modem control MPU)IC314 is an 8M bit Flash memory and contains the firm-ware of the Modem control MPU, RX DSP, and TX_Vocoder_DSP.■ SDRAMIC704 and IC707 are program execution 128M bit memo-ry used by the Main MPU.33BU33SH33SHIC700 IC719IC70333SH100K100K100KD16C_RST33SHIC70833MPUIC314IC32550MPUIC3433SH33SH33MPUIC30333MPU33MPU33MPUDSP_RSTRESET_DIC32433MPUIC32350MPUIC3550MPUWPADSP_RSTIC3733SHIC1750MPUEEPROMeachRF unit33SH33SHIC70250MPU33SHfrom RTESYS_RST47K33MPU50MPUWPFig. 26 Reset circuitCIRCUIT DESCRIPTION