Specifications

XT55 Hardware Interface Description
Confidential / Preliminary
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XT55_hd_v00.02 Page 18 of 116 17.03.2004
2 Product concept
Designed for use on any GSM network in the world, Siemens XT55 is a tri-band GSM/GPRS
engine that works on the three frequencies GSM 900 MHz, GSM 1800 MHz and GSM
1900 MHz and supports also GPS technology for satellite navigation. XT55 features GPRS
multislot class 10 and supports the GPRS coding schemes CS-1, CS-2, CS-3 and CS-4.
The compact design of the XT55 module makes it easy to integrate GSM / GPRS and GPS
as an all-in-one solution. It saves significantly both time and cost for integration of additional
hardware components.
The integrated GPS module provides instant location information using satellite signals to
enable users to ascertain where they are anywhere in the world. It consists of a fully
integrated RF receiver and a 12 channel baseband.
The tiny XT55 module incorporates all you need to create high-performance GSM/GPRS
solutions: baseband processor, power supply ASIC, complete radio frequency circuit
including a power amplifier and antenna interface. The power amplifier is directly fed from
the supply voltage GSM_BATT+. A compact “stacked FLASH / SRAM” device stores the
XT55 software in the flash memory section, and static RAM section provides the additional
storage capacity required by GPRS connectivity.
The physical interface to the cellular application is made through a board-to-board
connector. It consists of 80 pins, required for controlling the unit, receiving GPS location
data, transferring data and audio signals and providing power supply lines.
XT55 comprises two serial GSM interfaces (ASC0 and ASC1) and two serial GPS interfaces
(Serial data 1 and Serial data 2) giving you maximum flexibility for easy integration with the
Man-Machine Interface (MMI).
An extremely versatile audio concept offers various audio interfaces, each available on the
board-to-board connector: a digital audio interface (DAI) and two analog audio interfaces.
Using AT commands you can easily switch back and forth and select different audio modes.
The external dual-band or triple-band GSM/GPRS antenna can be connected optionally to a
connector on the top side or to a pad on the bottom side. A separate GPS antenna must be
connected to the GPS part of the module in order to properly receive satellite data.
For battery powered applications, XT55 features a charging control which can be used to
charge a Li-Ion battery. The charging circuit must be implemented outside the module on the
application platform.