All UARTs provide the following functions:
- Re-initialise a UART after it has been turned off.
- Disables the UART once all pending transmissions have finished.
- Registers a callback function that is called when a character is received by the UART.
- Remove any associated call back function for this UART.
- Returns FALSE if the UART has nothing left to send.
- Flushes the receive buffer - ie discards any received characters.
- Flushes the transmit buffer - ie it discards any outstanding bytes.
- Tests if the receive buffer is empty.
The following classes provide additional functionality