Description: The system is a simple to use timer 8253, 8255 parallel communication interfaces and interrupt controller 8259 designed electronic clock system has a start button in the system, the start button is not pressed, the display initialization interface " HELLO" when you press the start button, the timer starts counting 8253 (initial value of 8253 to 10000, then 1MHz pulse, that is when the 8253 count is just over 100 1S), when the timer count over 100, 8259 will generate an interrupt , the LED display will show the initial value of the pre-designed system " 23.59.55" started second position start plus 1, when applied to the 10S, 10s-bit plus 1 plus 1 bit is added to 60S division, while second bit is cleared zero, how was added 24 points while all clear.
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dianzishizhong.txt
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