S35390A_ALRM_BYTE_WDAY
buf[S35390A_ALRM_BYTE_WDAY] = bin2bcd(alm->time.tm_wday) | 0x80;
buf[S35390A_ALRM_BYTE_WDAY] = 0;
if (buf[S35390A_ALRM_BYTE_WDAY] & 0x80)
bcd2bin(buf[S35390A_ALRM_BYTE_WDAY] & ~0x80);