UPSTAT_CTS_ENABLE
uport->status |= UPSTAT_CTS_ENABLE;
uport->status &= ~UPSTAT_CTS_ENABLE;
return !!(uport->status & UPSTAT_CTS_ENABLE);
upstat_t mask = UPSTAT_CTS_ENABLE | UPSTAT_AUTOCTS;
return ((uport->status & mask) == UPSTAT_CTS_ENABLE);