IO (SOUND LIST)                                      PAGE  I6
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          FREQUENCY CONTROL   (for generators 0, 1, 2)
          -----------------
          Two bytes must be transmitted to the SGC for a given register
          and to compute the number of counts from the frequency F
          use: N = 111860 / F
 
          Binary     1-REG#-N(1s 4 bits)-00-N(ms 6 bits)
                            Note that N must be split up into its least
                            significant 4 bits and most significant 6
                            bits (10 bits total).
 
           The lowest frequency possible is 110 Hz and the highest is
          55938 Hz.
 
          NOISE CONTROL                 |
          -------------                 |
          One byte must be transmitted to the SGC:
 
          Binary     1-1-1-0-0-T-S
 
                T = 0 for white noise, 1 for periodic noise;
                S = Shift rate (0,1,2,3) = frequency center of noise.
                    S=3=frequency dependent on the frequency of tone
                    generator #3.