dsk 5402: a problem with expansion peripheral interface

Hello all, I'm using 5402 dsk and I'm trying to write words over a AD codec which is in daughter board.
I'm using Mcbsp0 as a serial port and I have written 1 to Lsb bit in the Cntl2 register. When I use this instruction: MCBSP_write16 (mhMcbsp,dato) I don't see anythin in the dx pin (number 24) in the expansion peripheral interface with the oscilloscope.
Must I use any instruction else? Does anyone have a C code in which pin dx is used?
Thanks
Note: I can give you my C code to have a look if you want.