Transmit Holding Regiter. The next character to be transmitted is written here (DLAB =0).
THR | Writing to the UARTn Transmit Holding Register causes the data to be stored in the UARTn transmit FIFO. The byte will be sent when it reaches the bottom of the FIFO and the transmitter is available. |
RESERVED | Reserved. Read value is undefined, only zero should be written. |