ST20-GP6
1 Introduction
The ST20-GP6 is an application-specific single chip micro using the ST20 CPU with
microprocessor style peripherals added on-chip. It incorporates DSP hardware for processing the
signals from GPS (Global Positioning System) satellites.
The twelve channel GPS correlation DSP hardware is designed to handle twelve satellites, two of
which can be initialized to support the RTCA-SC159 specification for WAAS (Wide Area
Augmentation Service) and EGNOS (European Geostationary Navigation Overlay System)
services.
The ST20-GP6 has been designed to minimize system costs and reduce the complexity of GPS
systems. It offers all hardware DSP and microprocessor functions on one chip and provides
sufficient on-chip RAM and ROM. The entire analogue section, RF and clock generation are
available on a companion chip. Thus, a complete GPS system is possible using just two chips, see
Figure 1.1.
Antenna
ST20-GP6
STB5600
Radio
Single chip
DSP
ASIC
Low
cost
crystal
No TCXO
CPU
Watchdog
timer
UART
Parallel
I/O
Real
time
clock
optional
mask ROM
RAM
Driver
(optional)
Parallel I/O
Figure 1.1 GPS system
The ST20-GP6 supports large values of frequency offset, allowing the use of a very low cost
oscillator, thus saving the cost of a Temperature Controlled Crystal Oscillator (TCXO).
The CPU and software have access to the part-processed signal to enable accelerated acquisition
time.
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