Nokia NSE–3 SERIES Service Manual

Contents

Nokia NSE–3 SERIES Service Manual Manual pdf 38 page image

PAMSTechnical DocumentationNSE–3System ModuleOriginal 11/97Page 3 – 32Internal Audio ConnectionsThe speech coding functions are performed by the DSP in the MAD2 andthe coded speech blocks are transferred to the COBBA–GJ for digital toanalog conversion, down link direction. In the up link direction the PCMcoded speech blocks are read from the COBBA–GJ by the DSP.There are two separate interfaces between MAD2 and COBBA–GJ: aparallel bus and a serial bus. The parallel bus has 12 data bits, 4 addressbits, read and write strobes and a data available strobe. The parallel inter-face is used to transfer all the COBBA–GJ control information (both theRFI part and the audio part) and the transmit and receive samples. Theserial interface between MAD2 and COBBA–GJ includes transmit and re-ceive data, clock and frame synchronisation signals. It is used to transferthe PCM samples. The frame synchronisation frequency is 8 kHz whichindicates the rate of the PCM samples and the clock frequency is 1 MHz.COBBA is generating both clocks.4–wire PCM Serial InterfaceThe interface consists of following signals: a PCM codec master clock(PCMDClk), a frame synchronization signal to DSP (PCMSClk), a codectransmit data line (PCMTX) and a codec receive data line (PCMRX). TheCOBBA–GJ generates the PCMDClk clock, which is supplied to DSP SIO.The COBBA–GJ also generates the PCMSClk signal to DSP by dividingthe PCMDClk. The PCMDClk frequency is 1.000 MHz and is generatedby dividing the RFIClk 13 MHz by 13. The COBBA–GJ further divides thePCMDClk by 125 to get a PCMSClk signal, 8.0 kHz.LSBLSBPCMDClkPCMSClkPCMTxDataPCMRxDataMSBMSB15 14 13 12 011 10sign extendedsign extended