CDNC_UART_MODEM_CTRL_REG
WR4(bas, CDNC_UART_MODEM_CTRL_REG, CDNC_UART_MODEM_CTRL_REG_DTR |
modem_ctrl = RD4(bas, CDNC_UART_MODEM_CTRL_REG) &
WR4(bas, CDNC_UART_MODEM_CTRL_REG, modem_ctrl);
modem_ctrl = RD4(bas, CDNC_UART_MODEM_CTRL_REG);
WR4(bas, CDNC_UART_MODEM_CTRL_REG, modem_ctrl);