These are the steps necessary to produce a steady tone:

   1. Define the waveform.
   2. Create the data set containing the pairs of data samples (data
      words). Normally, a data set contains the definition of one
      waveform.
   3. Set the location registers:

          audxlch  (high three bits)
          audxlcl  (low fifteen bits)

   4. Set the length register,  audxlen , to the number of data words to
      be retrieved before starting at the address currently in  audxlc .
   5. Set the volume register,  audxvol .
   6. Set the period register,  audxper 
   7. Start the audio DMA by writing a 1 into bit 9,  dmaen  , along with
      a 1 in the  set/clr  bit and a 1 in the position of the  audxen  bit
      of the channel or channels you want to start.