point-to-point XBEE


I have two XBEE modules, each controlled by an CPLD.
Both are configured in wireless UART, with X-CTU.
The ‘write’ with X-CTU is successfully completed.

One of the CPLD’s sends a UART sequence (start_bit + 8data + stop_bit) into one of the XBEE modules.
The other one receives data, but always sends out wrong data thru DOUT. The wrong data pattern is 0x7E, which means that all UART data bits are HIGH.

I probed the DI pin of the sender with logic analyzer, and found the UART is correct, 9600 baud, with expected data pattern. The expected data is 0x32 (correct data).

My question: why the RX XBEE always sends out 0x7e thru DOUT although the TX XBEE DI is 0x32?

Thank you for your help,