User Guide

PAMS
Technical Documentation
NSE–5
System Module
Page 2 – 33
Issue 1 07/99
Analog Audio Accessory Detection
In XEAR signal there is a 47 k pullup in the transceiver and 6.8 k
pull–down to SGND in accessory. The XEAR is pulled down when an
accessory is connected, and pulled up when disconnected. The XEAR is
connected to the HookDet line (in MAD), an interrupt is given due to both
connection and disconnection. There is filtering between XEAR and
HookDet to prevent audio signal giving unwanted interrupts.
External accessory notices powered–up phone by detecting voltage in
XMIC line. In Table 9 there is a truth table for detection signals.
Table 9.
Accessory connected HookDet HeadDet Notes
No accessory connected High High Pullups in the transceiver
Headset HDC–9 with a button switch
pressed
Low Low XEAR and XMIC loaded (dc)
Headset HDC–9 with a button switch re-
leased
High Low *) XEAR unloaded (dc)
Handsfree (HFU–1) Low High XEAR loaded (dc)
Internal Audio Connections
The speech coding functions are performed by the DSP in the MAD2 and
the coded speech blocks are transferred to the COBBA–GJP for digital to
analog conversion, down link direction. In the up link direction the PCM
coded speech blocks are read from the COBBA–GJP by the DSP.
There are two separate interfaces between MAD2 and COBBA–GJP: a
parallel bus and a serial bus. The parallel bus has 12 data bits, 4 address
bits, read and write strobes and a data available strobe. The parallel
interface is used to transfer all the COBBA–GJP control information (both
the RFI part and the audio part) and the transmit and receive samples.
The serial interface between MAD2 and COBBA–GJP includes transmit
and receive data, clock and frame synchronisation signals. It is used to
transfer the PCM samples. The frame synchronisation frequency is 8 kHz
which indicates the rate of the PCM samples and the clock frequency is 1
MHz. COBBA is generating both clocks.
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–GJP generates the PCMDClk clock, which is supplied to DSP
SIO. The COBBA–GJP 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–GJP further
divides the PCMDClk by 125 to get a PCMSClk signal, 8.0 kHz.