Description: Simple keyboard, use the keyboard to 1,2,3,4,5,6,7,8 eight keys, issued eight different tone, and asked to press the button sound, release delay for some time to stop the middle and then the other key is made of another tone of voice. When the system scans the keyboard key is pressed to quickly detect which key is pressed, then the MCU timer is activated, emits a certain frequency of pulse, the frequency of the pulse amplifying and filtering by the speaker drive circuit, will send the appropriate tone. If the previous key pressed sound at the same time another key is pressed, the interrupt system is enabled, stopped in front of key pronunciation, pronunciation program go to press the key issue after key press sound.
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dianziqin.asm
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