Datasheet

SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
340
16.6.2 RTC Mode Register
Name: RTC_MR
Address: 0x400E1864
Access: Read/Write
This register can only be written if the WPEN bit is cleared in the System Controller Write Protection Mode Register
(SYSC_WPMR).
 HRMOD: 12-/24-hour Mode
0: 24-hour mode is selected.
1: 12-hour mode is selected.
 PERSIAN: PERSIAN Calendar
0: Gregorian calendar.
1: Persian calendar.
 NEGPPM: NEGative PPM Correction
0: Positive correction (the divider will be slightly higher than 32768).
1: Negative correction (the divider will be slightly lower than 32768).
Refer to CORRECTION and HIGHPPM field descriptions.
Note: NEGPPM must be cleared to correct a crystal slower than 32.768 kHz.
 CORRECTION: Slow Clock Correction
0: No correction
1–127: The slow clock will be corrected according to the formula given below in HIGHPPM description.
 HIGHPPM: HIGH PPM Correction
0: Lower range ppm correction with accurate correction.
1: Higher range ppm correction with accurate correction.
If the absolute value of the correction to be applied is lower than 30 ppm, it is recommended to clear HIGHPPM. HIGHPPM
set to 1 is recommended for 30 ppm correction and above.
Formula:
If HIGHPPM = 0, then the clock frequency correction range is from 1.5 ppm up to 98 ppm. The RTC accuracy is less
than 1 ppm for a range correction from 1.5 ppm up to 30 ppm.
The correction field must be programmed according to the required correction in ppm; the formula is as follows:
31 302928 27 26 25 24
– – TPERIOD – THIGH
23 22 21 20 19 18 17 16
–OUT1–OUT0
15 14 13 12 11 10 9 8
HIGHPPM CORRECTION
76543 210
– – – NEGPPM – – PERSIAN HRMOD