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答：因为要对寄存器进行读写！而在STM32中对寄存器的读写都是要打开寄存器对应的时钟才可以的【就像人一样，有了跳动的脉搏手臂才能有能量才能进行各种动作】。 接下来：跟AFIO相关的寄存器有哪些呢？ 应用：在usart1串口通信没有端口重映射时为什么不打开AFIO时钟？PA9、PA10作为通用I/O口也复用了，为什么不打开为什么不打开复用时钟？ To optimize the number of peripherals available for the 64-pin or the 100-pin or the 144-pin package, it is possible to remap some alternate functions to some other pins. This is achieved by software, by programming the AF remap and debug I/O configuration register(AFIO_MAPR) on page 159. In this case, the alternate functions are no longer mapped to their original assignations.
可见AFIO就设计用来remap some alternate functions to some other pins的，所以根本就没有什么“复用”之说，看来都是翻译惹的祸！另外看一下I/O复用时的情况就更清楚了
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楼主
