单片机的一个机器周期是指完成某一个规定操作所需的时间，一般情况下，一个机器周期等于一个时钟周期组成。
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51单片机复位后，P1口的引脚为高电平。
A. 对
B. 错
单片机最小系统是指单片机能够工作的最小电路，一般包括电源电路、时钟电路和复位电路。
A. 对
B. 错
Where did J.K. Rowling come up with the idea for Harry Potter?
At a café
B. On a train.
C. At a cinema.
D. In a bookstore.
What areJ.K. Rowling's further plans?
A. She won’t write any more books.
B. She will write more magic stories.
C. She hasn’t said anything about her future plans.
D. She said she would work on more serious subjects.
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