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1, for A specific D/A transformation interface circuit, the CPU to execute A command to output data into D/A, in its output terminal can get certain voltage output. To D/A converter input according to the data, regular changes in the sine in its output terminal can produce sine wave. For music, each scales have certain frequency.
The scales nominal frequency value:
Note 1 2 3 4 5 order 6 7
Frequency (unit: 261.1 293.7 329.6 Hz ac) 349.2 392.0 440.0 493.9
2, produce A sine wave data desirable 32 (less than), also of different frequency difference, but through the adjustment to D/A converter output data intervals of time, such as: hair "1" frequency of 261.1 HZ ac, cycle for 1/261.1 = 3.83 ms, output data intervals of time of 3.83 ms/ms 32 = 0.12. Timing can be made by 8253 with 8255 time to realize. Press a key pronunciation by the length of time a sine wave can be the number to control how much.
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dianziqin.cpp
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