CDNC_UART_FIFO
WR4(bas, CDNC_UART_FIFO, c);
c = RD4(bas, CDNC_UART_FIFO);
WR4(bas, CDNC_UART_FIFO, sc->sc_txbuf[i]);
c = RD4(bas, CDNC_UART_FIFO) & 0xff;