SER_DDTR
if (sig & SER_DDTR) {
SIGCHG(sig & SER_DTR, new, SER_DTR, SER_DDTR);
if (sig & SER_DDTR) {
new = (new & ~SER_DTR) | (sig & (SER_DTR | SER_DDTR));
if (sig & SER_DDTR) {
SER_DDTR);
if (sig & SER_DDTR) {
SER_DDTR);
UART_SETSIG(sc, SER_DDTR | SER_DRTS);
UART_SETSIG(sc, SER_DDTR | SER_DRTS);
UART_SETSIG(sc, SER_DDTR | SER_DTR);
if (sig & SER_DDTR) {
SIGCHG(sig & SER_DTR, new, SER_DTR, SER_DDTR);