I believe I have got the answer with your and TI tech support's help. The problem of
MCBSP_write16() is that it only sent data to DXR, and a long way from XSR to DX is left
unsupervised by the code. If one want to write one UINT16 by McBsp and then close the McBsp. I
believe the following is the best way to do it.

    while (!MCBSP_xrdy(hMcbsp1));
    MCBSP_write16(hMcbsp1, 0x3579);  // 0x3579, data intended to write, goes to XSR
    while (!MCBSP_xrdy(hMcbsp1));
    MCBSP_write16(hMcbsp1, 0x1111);  // 0x1111, dummy data, to DXR; 0x3579 goes to XSR
    while (!MCBSP_xrdy(hMcbsp1)); // dummy data goes to XSR, and 0x3579 is shipped out by DX
    MCBSP_close(hMcbsp1); 

Thanks to Jeff and Dileepan.
	

Li Wei-

> I believe I have got the answer with your and TI tech support's help. The
> problem of MCBSP_write16() is that it only sent data to DXR, and a long
> way from XSR to DX is left unsupervised by the code. If one want to write
> one UINT16 by McBsp and then close the McBsp. I believe the following is
> the best way to do it.
>
>     while (!MCBSP_xrdy(hMcbsp1));
>     MCBSP_write16(hMcbsp1, 0x3579);  // 0x3579, data intended to write,
> goes to XSR
>     while (!MCBSP_xrdy(hMcbsp1));
>     MCBSP_write16(hMcbsp1, 0x1111);  // 0x1111, dummy data, to DXR;
> 0x3579 goes to XSR
>     while (!MCBSP_xrdy(hMcbsp1)); // dummy data goes to XSR, and 0x3579
> is shipped out by DX
>     MCBSP_close(hMcbsp1);

Yes this looks very reasonable.  My one comment would be to add some
time-out (escape) to the while loop in case the serial link breaks (other
end disconnects).  From a high-level system perspective, at the time of
"closing" the McBSP port, anything could be happening.

-Jeff