基于Intel 8253定时器的两端Asm，包括配套电路，流程图
1。设计基于ISA总线的Intel 8253 的接口电路，用Intel 8253 的1个通道作定时器，演奏C调的各个音符，利用查表程序的方法依次演奏，每个音符演奏1s，停0.5s 演奏三遍后退出程序
2。利用Intel 8253的一个通道产生一个100Hz的方波，用示波器测试信号的正确性
以产生的方波作为另一个通道门控信号。利用此通道测量其高电平的宽度，在PC机显示屏上显示其数值并退出程序
-based on the Intel 8253 timer at both ends of programmers, including matching circuit, flowchart
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