NSW-6
System Module SE2
PAMS Technical Documentation
Page 34
Issue 1 12/99
Nokia Mobile Phones Ltd.
4–wire PCM Serial Interface
The interface consists of following signals: a PCM codec master clock
(PCMDClk), a frame synchronization signal to DSP (PCMSClk), a codec
transmit data line (PCMTX) and a codec receive data line (PCMRX). The
COBBA_D generates the PCMDClk clock, which is supplied to DSP SIO.
The COBBA_D also generates the PCMSClk signal to DSP by dividing the
PCMDClk. The PCMDClk frequency is 1.000 MHz and is generated by
dividing the RFIClk 13 MHz by 13. The COBBA_D further divides the
PCMDClk by 125 to get a PCMSClk signal, 8.0 kHz.
LSB
LSB
PCMDClk
PCMSClk
PCMTxData
PCMRxData
MSB
MSB
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14
13
12
0
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10
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The output for the internal earphone is a dual ended type output capable
of driving a dynamic type speaker. The output for the external accessory
and the headset is single ended with a dedicated signal ground SGND.
Input and output signal source selection and gain control is performed
inside the COBBA_D asic according to control messages from the
MAD1PR1. Keypad tones, DTMF, and other audio tones are generated
and encoded by the MAD1PR1 and transmitted to the COBBA_D for
decoding. MAD1PR1 generates two separate PWM outputs, one for a
buzzer and one for vibra (internal and external via BTEMP).
Speech Processing
The speech coding functions are performed by the DSP in the MAD1 and
the coded speech blocks are transferred to the COBBA_D for digital to
analog conversion, down link direction. In the up link direction the PCM
coded speech blocks are read from the COBBA_D by the DSP.
There are two separate interfaces between the MAD and the COBBA: 2
serial buses. The first serial interface is used to transfer all the COBBA
control information (both the RFI part and the audio part). The second
serial interface between the MAD and COBBA includes transmit and
receive data, clock and frame synchronization signals. It is used to
transfer the PCM samples. The frame synchronization frequency is 8 kHz
( the sample rate is in digital mode 8.0 kHz and in analog mode 8.1 kHz)
which indicates the rate of the PCM samples and the clock frequency is 1
MHz. The COBBA is generating both clocks.
