C_RS_DCD
if (ISSET(rs_status, C_RS_DCD))
sc->sc_chanctl_hw_flow = C_RS_DCD | C_RS_DTR;
(void) (*linesw[tp->t_line].l_modem)(tp, ISSET(rs_status, C_RS_DCD));
ISSET(C_RS_DCD, CZTTY_CHAN_READ(sc,