Specifications

24
The position and velocity accuracy are shown in the following table, assuming full
accuracy C/A code.
Parameter Value
Horizontal CEP 2.2 m
Horizontal (2 dRMS) 5.5 m
Vertical VEP 2.0 m
3.9. RTC
V3020 chip provides RTC functionality on the EM-X270. The real-time clock/calendar
provides seconds, minutes, hours, day, date, month, year and century information. A
time/date programmable polled ALARM is included. The end-of-the-month date is
automatically adjusted for months with fewer than 31 days, including corrections for leap
year up to the year 2100. The clock operates in either 24hr or 12hr format with an AM/PM
indicator.
Setting the time and date of V3020 RTC is supported through Linux and Win CE packages
provided for the EM-X270.
Interface
The V3020 RTC uses a single line serial I/O interface, implemented using standard R/W
operations and an MD[0] local bus data line at physical address 0x10000000 in the PXA-
270 CPU memory space.
The RTC chip’s power supply is connected both to the main battery and to the onboard
back-up coin cell battery. Thus, the RTC data is preserved even when the main battery is
detached from EM_X270. See section 3.10 for a more detailed explanation.