Dear All, My requirement is: If a particular byte is received thro UART0, I have to do some action which will take more than 500 ms. I cant do those actions in the ISR itself as it takes a long time.So I wrote a function to do those actions and call it from the ISR when the particular byte is received. My problem is that particular byte may be received second time before those actions get finished for the particular byte received for the first time. so it makes the UART0 ISR as recursive. Does it cause any problem? Any other suggestions to solve the problem? Note: 1) Those actions may use the UART0 2) I cant do polling.