UART issue in API mode

Hi all, I bought a Texas Instrument C2000 proccessor, with UART port, i am interfacing with xbee S2 by sci-a port. As you know Xbee has two modes, either AT or API.

First I make my own “hello world” in AT mode with twice xbee (they are configured correctly). if i send a message, always in AT mode, transmission works fine, I can be able to receipt or send any AT command (like ATP105). But, in API mode, it’s impossible, I tried send command frame API and doesnt works.

Also, sniffing UART port I can see the correct API frame, 7E 00 05 08 01 50 31 04 71.
baud rate is 9600, no parity, 8bit word, no handshake and one stop bit.

some advice? The important deal is: why I can send any command in AT mode, but API not?

Best regards