1、对于一个特定的Ｄ/Ａ转换接口电路，CPU执行一条输出指令将数据送入Ｄ/Ａ，即可在其输出端得到一定的电压输出。给Ｄ/Ａ转换器输入按正弦规律变化的数据， 在其输出端即可产生正弦波。对于音乐，每个音阶都有确定的频率。

各音阶标称频率值：

音 阶　　 1　　 2　　 3　　 4　　 5　　 6　　 7

频率(单位:Hz)　　261.1　　293.7　　329.6　　349.2　　392.0　　440.0　　493.9



2、产生一个正弦波的数据可取32个（小于亦可），不同频率的区别，可通过调节向Ｄ／Ａ转换器输出数据的时间间隔，例如:发"１"频率为261.1HZ，周期为 1/261.1 = 3.83ms，输出数据的时间间隔为 3.83ms/32 = 0.12ms。定时时间可以由8253配合8255来实现。按下某键后发音时间的长短可以由发出的正弦波的个数多少来控制。

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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.