reading a port is just one instruction. But then you have to move the data to the ram location. so to be conservative, I would say it is a 2-3 cycles. That means if you are running at 4Mhz, you can read about one byte every 2 - 3 us.

then the math is simple after that.

回复【2楼】millwood0  
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thanks for your answer!

回复【1楼】headwolf_83  
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噢,可能是我没表达清楚,我要用单片机从A/D芯片读取结果,速率要在1M左右

只是读取数据还不简单。指令时间=时钟/4。如果只是读一下。只要支持4M以上时钟的PIC单片机就可以了。