Hello : I am using a PIC18 and a MCP2510 in order to communicate with other systems through the CAN bus. When the MCP2510 receives a message, the PIC gets the CAN message from the MPC2510, processes it and sends back the answer. The PIC does all that in the interrupt service routine. This could take a while and the PIC also have to serve other interrupts (like send and receive characters via usart). So I am undecided between prioritized interrupts, or single interrupt priority using a flag to do the CAN communication outside the ISR. Any thoughts? Regards, Carlos -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.