pin configuration

基本解释

The selected function for the GP3/MCLR pin is input, and you must enable the global weak-pullup bit in the microcontroller's configuration word.
GP3/MCLR管脚的可选功能为输入，在微处理器配置命令中，必须使能全局弱上拉位。
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Optional user-supplied clock input. Synchronizes the initialization of one or more devices. This pin can be used as a user I/O pin after configuration.
用户可选的时钟输入。同步一个或多个芯片的初始化（配置）。在配置完成后这个管脚可以当做普通的I/O口。
blog.sina.com.cn
Research includes as following: MIFARE 1 card features, functional composition, storage structure and MIFARE 1 card reading equipment core modules features, pin configuration, operating principles.
研究内容包括：MIFARE 1射频卡的特点、功能组成、存储结构以及MIFARE 1卡读写设备核心模块的特点、管脚排列、工作原理等。