To provide efficient processing of interrupts, Windows CE splits interrupt handling into two distinct parts: an interrupt service routine (ISR) and an interrupt service thread (IST). When triggered, the ISR does little more than launch the IST that is responsible for handling the event. Once the IST has been launched, the ISR returns and the system can respond to the next interrupt.
Dividing interrupt handling this way allows the ISR to be very small and fast. This minimizes interrupt latencies and speeds interrupt processing. The Windows CE Embedded Toolkit for Visual C++ makes it possible for you to specify interrupt timing and priorities for a specific platform.