1. As mentioned in the datasheet (the snippet you have added) you must not clear the interrupt for RX FIFO not empty or TX FIFO not full as these are automatically cleared by the component. Hence, the statements within UartIntHandler must be removed.
Q2:In the datasheet, there is the description "The External interrupt mode is preferred in this case.".
But if I set RX buffer size or TX buffer size greater than the FIFO depth, I can not select the external interrupt.
What does this mean?
Please check the statement above that.
"In case RX buffer size or TX buffer size is equal to the FIFO depth only the hardware TX or RX FIFO is used. In the Internal interrupt mode the interrupts are not cleared automatically. It is the user’s responsibility to do this. The External interrupt mode is preferred in this case."
It is only if hardware FIFO is used that external interrupts are available and preferred. If software FIFO is used, that is, Buffer size > 16 bytes in byte, mode this option is unavailable and internal interrupt is enabled.
Thank you very much.
I can understand all.
Since there is no interrupt enable in the sample code, just add the following.