Your code doesn't poll the RI bit of the serial port.

therefore I would suggest something like this:

while(1)
{
if (RI)
{
daout(SBUF);
RI = 0;
}
}

Be aware that the data from the serial port is only 8 bits, so your dac will need to be setup accordingly or scale the 8 bits up to the 12bit value for the dac. I haven't used the aduc814 so I can't comment exactly on the operation of the DAC.

You will need some low pass filtering on the output of the DAC to clean up the output.

I don't know what you application is, but there are probably better means of transporting audio digitally than the method you've proposed. In fact there's chips designed specifically for this.