Rainbow Electronics ATR0620 - Manual (Page 12)

12
4574CS–GPS–05/05
ATR0620 [Preliminary]
12. SF: Special Function
The ATR0620 provides registers that implement the following special functions:
• Chip identification
• RESET status
13. PWM
The PWM includes two PWM channels. They can be programmed separately. It is possible to
generate an output voltage range from 0 to (255/256)
×
VDD18.
14. RTC
The RTC provides the time in GPS format. The structure of the GPS system time: zero point is
midnight Universal Time (UT) 5
th /6 th of January 1980. From the zero point weeks, time of week
and the 15-bit fractional part of a second are counted. Each week has 604800 seconds (GPS
system time does not count leap seconds. Therefore, compared to UT, the GPS time is shifted
some seconds).
Additional the RTC provides a programmable interrupt (maximum period: one week).
15. GPS Correlator
The GPS correlator incorporates 16 GPS channels and provides all the functionality required for
sampling, down-converting and correlating GPS signals.
The GPS correlator processes GPS signal data to acquire the GPS satellite signals using a
model of the satellite codes and multiply/accumulate circuits (correlators) to spread the signal to
a bandwidth low enough to detect it above thermal noise.
16. GPS Accelerator
The ATR0620 features an accelerator which reduces the time to identify the correct GPS signal.