Kenwood NX-740H Service Manual page 15

2.4.6.3 NXDN Receiving
• For Digital Data Mode:
The demodulated signal from IC501 (Pin13) feed into baseband IC (Pin 16) for NXDN decoding.
The decoded digital data will pass to MCU through C-BUS. MCU determines whether or not to output sound from speaker by check-
ing if the data match.
• For Digital Voice Mode:
If the digital data match in MCU, the digital voice payload data will goes into Vocoder in MCU for conversion to PCM.
The PCM data will go to baseband IC through SPI input, where it will be converted to analog by DAC.
Analog voice will be filtered and finally send to audio amplifier.
IC501
IF IC
2.4.6.4 NXDN Transmitting
• For Digital Data Mode:
The digital data will be generated by MCU, where it wil be pass to baseband IC, through C-BUS for encoding process. The encoded
data finally will transmit through TCXO and VCO modulation.
• For Digital Voice Mode:
The analog voice from mic will go to ADC (after audio filter) to convert to PCM data.
The PCM data will send to Vocoder through SPI output.
Vocoder will convert the PCM to NXDN protocol, where it will be sent to baseband through C-BUS.
In baseband IC, the data will be encoded and finally transmit through TCXO and VCO modulation.
TCXO
IC709 Baseband IC
13 16
NXDN
decoder
Audio
Output
To E-Vol
Fig.14 NXDN receiver system
IC709 Baseband IC
23
NXDN
encoder
24
VCO
Audio
Filter
From MIC
Fig.15 NXDN transmit system
43 75
C-BUS C-BUS
3 112
Vocoder
SPI
IC714 MCU
42 76
C-BUS C-BUS
1 113
Vocoder
SPI
IC714 MCU
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