AT91_RTC_NEGPPM
if (!(mr & AT91_RTC_NEGPPM))
mr &= ~(AT91_RTC_NEGPPM | AT91_RTC_CORRECTION | AT91_RTC_HIGHPPM);
mr |= AT91_RTC_NEGPPM;
at91_rtc_write(AT91_RTC_MR, mr & ~AT91_RTC_NEGPPM);