Description: Use AT89S51 microcontroller have a "tick, tick, ..." alarm sound from the P1.0 port output, resulting in a frequency of 1KHz, according to the above figure we can see: 1KHZ square-wave output of 0.2 seconds from the P1.0, followed by 0.2 seconds from the P1.0 output level signals, and so cycle continues, the result we need to sound the alarm.
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titi\实验18.doc
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