Undefineable NIOS reboot @ RS232 communication

Hi all!

I have a problem with my NIOS II application (Cyclon III) which communictes with a host application over RS232, and hope to get some

advices, maybe solutions, here! :-)

problem description:

1. Host application and NIOS UART (application) are adjusted to 9600kB -> communication ok

2. Both applications are set to 115200kB -> communication ok

3. NIOS UART stays at 115200kB and host application is adjusted back to 9600kB -> communication not ok, which is correct and expected :-)

-> When now permanently sending Data over the RS232 from the host application at 9600kB to the Nios Application which is still

adjusted to 115200kB it happens after some seconds, that the NIOS reboots ...!???

Data Reading from UART is done by Interrupt:

..

iowr_altera_avalon_uart_control(uart_0_base, altera_avalon_uart_control_rrdy_msk);

..

alt_irq_register (uart_0_irq, (void *)0, os_rxisrhandler);

alt_irq_enable (uart_0_irq);

..

Does anybody have an idea where this could come from, or how to prevent!?

Many thanks in advance,

marco