Starting with the simplest one i.e using the POLL method. The data is Received in blocking mode i.e the CPU will block every other operation until the data transfer is complete. This method is good to use if you are only using UART and nothing else otherwise all other operations will be affected.
UART have a feature called IDLE line detection and we are going to use this to sole the problem mentioned above. Idle line is detected on RX line when there is no received byte for more than 1 byte time length.
We continuously check for incoming data and when data is received, display it on the lcd. 2.) Use interrupt. Microcontroller does it's normal operations, and whenever the data receiving completes, an interrupt is generated and ISR is executed, after completing ISR, control returns back to normal operation.