RTC_REG_B
reg_b = CMOS_READ(RTC_REG_B) & 0x7f;
CMOS_WRITE(reg_b, RTC_REG_B);
CMOS_READ(RTC_REG_B) == reg_b) {
val = CMOS_READ(RTC_REG_B);
CMOS_WRITE(val, RTC_REG_B);
val = CMOS_READ(RTC_REG_B);
CMOS_WRITE(val, RTC_REG_B);
#define RTC_CONTROL RTC_REG_B