hi,
I programmed serial port in mode0

Do you need with Mode 0 really? Do you know how UART works in this mode?
I mean that UART in mode 0 is just simple shift register. It means that it transmits and receives bit stream through RX pin. TX pin is used for transmit shift clock only! Maybe to receive data, you use TX pin as input, don`t you? In this case, if RX pin receives high level so byte comes in as 0xFF.
Once again: in Mode 0 UART receives data with RX pin opposite to its other modes. TX is used as source of shitf clock for both receive and transmit tasks.

Regards,
Oleg