- Serial interface is used.
The audio interface and the baseband-RF interface converters are integrated into the COBBA circuit.
The codec includes the microphone and earpiece amplifier and all the necessary switches for routing. There are 2 different possibilities for routing; internal and external devices. There are also all the AD- and DA-converters for the RF interface.
The DEMO block is used for FM-demodulation in analog mode.
A slow speed DA-converter provides the automatic frequency control (AFC). In addition, there is a DA-converter for the transmitter power control (TXC).
The COBBA also passes the RFC (19.44 MHz) to MAD as COBBACLK (9.72 MHz).
The COBBA is connected to the MAD via two serial buses:
- RXTXSIO, for interfacing the RF-DACs and DEMO; and also for audio codec and general control. Signals used: COBBACLK (9.72 MHz, from COBBA), COBBACSX, COBBASD (bi-directional data) and COBBADAX (data ready flag for rx-samples).
- Codec SIO, for interfacing the audio ADCs / DACs (PCM-samples). Signals: PCMDCLK (data clock 1.08 MHz / 1.215 MHz), PCMSCLK (frame sync 8.0 kHz / 8.1 kHz), PCMTxdata and PCMRxdata.
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