Strange effects of UART at reset

Hello,

I use an UART peripheral to communicate with a computer. If I launch the program, it works correctly, but if I reset the Nios II processor I have some problems. Here I post an simpler example where I have also the problem. The first code works correctly all the time, I receive well 1234 each time I reset the cpu.

int main (void)
{
    printf("1234 ");
    while(1);
}

But if i had the usleep function, that works when I launch the program, but if I reset the cpu, it the programs sends more characters than wanted.

int main (void)
{
    usleep(500000);
    printf("1234 ");
    while(1);
}

I received the following (one line by reset of cpu) :

1234

34 1234

1234 1234

234 1234 1234

4 1234 1234 1234

1234 1234 1234 1234

34 1234 1234 1234 1234

But if I have the usleep function and I remove the while(1), I receive well 1234. Anybody have an idea why I have these effects ?

Thanks in advance.

Jérôme