serial noise problem

[sandro]

I have some freeze when my system communicate via UART.
To test it I have ignected on it a square wave at 10Khz on it.
If I upply the disturbance first, then I read the serial port (cat /dev/ttyS0) system freeze.
If I open the serial then upply the disturbance the serial read some strange chapter but don't crash.
Someone can help me to solve it?
Thanks

[davidefa]

Ciao Sandro, have you disabled all the other tasks using the serial port?

[sandro]

Ciao Davide,
Yes, I have verified it by fuser and no program use it.
Beside, if the UART doesn't have disturbance, the communication is regular.