I need more information about the UART Triggering when we use UART_FCR register to set the Triggers. Whether the interrupt will hit after this Tigger level or before the trigger level. Please send the updated TRM. in the explanation of FIFO Interrupt Mode, there is diagram for interrupt generation of Rx and Tx, In that which register it is referring to. UART_IIR_UART or UART_ISR2.