AD20MSP410 Analog Devices, Inc., AD20MSP410 Datasheet - Page 4

• Manufacturer Part Number: AD20MSP410
• Description: Gsm Baseband Processing Chipset
• Manufacturer: Analog Devices, Inc.

AD20msp410
Automatic Frequency Control (AFC)
The mobile radio has to track precisely the master clock
provided by the base station. Drift of the crystal oscillator over
time and temperature has to be compensated as well as fre-
quency shifts due to the Doppler effect in the case of a moving
mobile radio. The received signal is analyzed in the ASP and the
PLP and a digital control signal is generated. This signal is sent
to the two DACs in the BBC. The 10-bit DAC operates as
coarse and the 8-bit DAC as fine adjust. The weighting of the
DACs is such, that both DACs yield a combined resolution of
13 bits. The combined analog output signal is used to control
the voltage controlled, temperature compensated crystal
oscillator (VCTCXO).
Synthesizer Control
The PLP and the respective parts of the Layer 1 software
control the overall timing and frequency generation of the radio
subsystem. This includes control signals for up to two synthesiz-
ers, powerdown control signals and power amplifier monitor
signals. Detailed information can be found in the ADPLP01
data sheet.
Generation of Auxiliary Audio Signals
Under control of Layer 1 the ASP 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 ASP also generates Talker Sidetone as specified in the
GSM recommendations. In comparison to traditional hardware
implementations, this software implementation provides manu-
facturing flexibility over a wide range of speaker/microphone
sensitivities.
Figure 3 shows the audio section and the auxiliary ADC of the
BBC. 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. Two output-PGAs can be pro-
grammed for –15 dB or +6 dB.
VOICEBAND
INTERFACE
INTERFACE
AUXILIARY
AUDIO/AUXILIARY SECTION
SERIAL
SERIAL
Figure 3. Audio-/Auxiliary Section of AD7015
FILTER
DAC
FILTER
DAC
10-BIT DAC
PGA
PGA
PGA
REFERENCE
VOLTAGE
MUX
MUX
CAR
KIT
LOCK
U
TEMP
OTHER
BAT
–4–
DATA SERVICES
Data Services is considered to be an essential feature for GSM
terminals and the AD20msp410 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. However, the chipset provides
full channel coding and decoding for all Data Services. Parity
and convolutional encoding and interleaving for TCH/F9.6,
TCH/F4.8 and TCH/F2.4 are implemented in the PLP.
The interface to the chipset is a user-configurable, 3-wire serial
interface 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) which 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 via
both traffic data and control information are communicated.
The Technology Partnership can provide all requisite Data
Services Software.
SOFTWARE IMPLEMENTATIONS
A full implementation of the GSM Layer 1 functionality is
supplied as an object code module, for execution on the
controller, embedded in the PLP. Functions performed by this
software include:
• Initial scan of GSM band and selection of strongest thirty
• Mobile oscillator adjustment, timing synchronization and
• Base station frequency and timing measurements and BSIC
• Frequency hopping according to 05.02
• Full implementation of discontinuous reception (DRX) and
• Reporting of received level and signal quality
APPLICATION LAYER
APPLICATION LAYER
PROTOCOL STACK
PROTOCOL STACK
channels as required by 03.22 and 05.08
BCCH decoding from serving cell (camping-on)
extraction from neighbor cells under control of Layer 3
transmission (DTX)
FOREGROUND
BACKGROUND
AD20msp410
LAYERS 2/3
LAYER 1
CHIPSET
Figure 4. Implementation of Data Services
HANDSET
INTERPRETER
COMMAND
ROUTER
FRAME
FRAMES
V110'
DATA TERMINAL
DATA TERMINAL
RADIO LINK PROTOCOL (RLP)
ADAPTER
MAN MACHINE INTERFSCE
EXTERNAL
ADAPTER
LAYER 2 RELAY (L2R)
DATA APPLICATION
RATE ADAPTION
REV. 0