I have a Spartan-3A DSP 1800 board, with one Microblaze on it. My software is witten above the operating system of µC/OS-II. The software has only one cyclic task that sends and receives continuously Ethernet frames in some specific format and order. EmacLite interrupts are used to send and receive frames. The software runs usually correctly; but it is often restarted unexpectly sooner or later after its starting. I tried to find problem in my single cyclic task. But I didn't find anything wrong. I wrote a simple program to test my cyclic task. The program has no operating system, but a single loop of the single cyclic task running once and again continuously with no timer. In this case, the single task runs correctly without any unexpected breakup or restart. I also tried to enlarge the stack. But it doesn't help either. The problem is always there. Besides, no dynamic memory is allocated and released in my single task. I am really confused what's the problem. Hopefully you could give me some hints. Thanks in advance.