C_RS_RTS
SET(czttybits, C_RS_RTS);
CLR(sc->sc_chanctl_rs_control, C_RS_DTR | C_RS_RTS);
if (ISSET(rs_status, C_RS_RTS))
sc->sc_chanctl_hw_flow = C_RS_CTS | C_RS_RTS;
sc->sc_rs_control_dtr = C_RS_DTR | C_RS_RTS;
SET(sc->sc_chanctl_rs_control, C_RS_RTS);
CLR(sc->sc_chanctl_rs_control, C_RS_RTS);
CZTTY_CHAN_WRITE(sc, CHNCTL_HW_FLOW, C_RS_CTS | C_RS_RTS);