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AD6421AST Scheda tecnica(PDF) 4 Page - Analog Devices |
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AD6421AST Scheda tecnica(HTML) 4 Page - Analog Devices |
4 / 8 page AD20msp415 –4– REV. 0 CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD20msp415 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. Generation of Auxiliary Audio Signals Under control of Layer 1, the GSMP can generate a variety of fixed and user-programmable tones. This includes all standard DTMF and Call Progress tones as well as user defined tones. The tone structure can consist of up to four frequency compo- nents with individual durations. The GSMP also generates Talker Sidetone as specified in the GSM recommendations. In comparison to traditional hardware implementations, this soft- ware implementation provides manufacturing flexibility over a wide range of speaker/microphone sensitivities. AD6421 SERIAL VOICE PORT SERIAL AUXILIARY PORT AUXILIARY ADC FILTER FILTER ADC PGA MUX CAR KIT U BAT TEMP OTHER ADC PGA MUX MUX Figure 3. Audio/Auxiliary Section of the AD6421 Figure 3 shows the audio section and the auxiliary ADC of the VBC. Input signals can come from either a directly connected microphone or from a remote microphone in a car kit. Input gain can be set to 0 dB or +26 dB. The output signal can be directly connected to a small earpiece and, for further amplifica- tion, to an external car kit. The output PGA can be programmed for –15 dB or +6 dB. DATA SERVICES Data Services is considered to be an essential feature for GSM terminals and the AD20msp415 chipset is designed to provide flexible and low cost implementation of Data Services supported via the GSM air interface. The selected system architecture shown in Figure 4 provides for minimum terminal Bill of Materials, the lowest possible number of interconnection points and the lowest power consumption when running speech traffic only. The GSMP performs full channel coding and decoding for TCH/F9.6, TCH/F4.8 and TCH/F2.4 data rates. The interface to the chipset is a user- configurable, 3-wire synchronous or asynchronous serial inter- face supplying V110´ data packets as defined in GSM 05.03, combined with protocol information and control to the Applica- tion Layer. External to the terminal is the Data Terminal Adapter (DTA) that runs the Data Services Software. Included in the DTA are the rate adaptation functions and the Data Services application. The Command Interpreter resident on the mobile supports a serial interface protocol with the DTA by which both traffic data and control information are communicated. V110' FRAMES MAN MACHINE INTERFACE DATA APPLICATION LAYER 2 RELAY (L2R) RADIO LINK PROTOCOL (RLP) RATE ADAPTION EXTERNAL DATA TERMINAL ADAPTER HANDSET APPLICATION LAYER FOREGROUND COMMAND INTERPRETER FRAME ROUTER DATA TERMINAL ADAPTER APPLICATION LAYER BACKGROUND PROTOCOL STACK LAYERS 2/3 PROTOCOL STACK LAYER 1 AD20msp415 CHIPSET Figure 4. Implementation of Data Services SOFTWARE IMPLEMENTATIONS A full implementation of the GSM Layer 1 functionality is sup- plied as an object code module, for execution on the controller, embedded in the GSMP. Functions performed by this software include: • Initial scan of GSM/E-GSM/PCN band and selection of strongest thirty channels as required by 03.22 and 05.08. • Mobile oscillator adjustment, timing synchronization and BCCH decoding from serving cell (camping-on). • Base station frequency and timing measurements and BSIC extraction from neighbor cells under control of Layer 3. • Frequency hopping according to 05.02. • Full implementation of discontinuous reception (DRX) and transmission (DTX). • Reporting of received level and signal quality. • Full engineering and test mode support. • Support for all phase 1 and phase 2 handover modes. • SIM Interface driver. • Message interfacing to Layer 3 (Radio Resources Manager) and Layer 2 (data link layer, both signaling and data). • External functions for AGC, AFC and synthesizer setting are called by Layer 1. These allow the user to configure the sys- tem for a wide range of radio architectures. The higher layers of the protocol stack also reside on this em- bedded processor. WARNING! ESD SENSITIVE DEVICE |
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