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w5500（SPI转以太网）和MCP2515（SPI转CAN）都自带晶振
应该是（外接晶体+芯片内部的谐振电路）
因为晶体需要连接谐振电路才能起振
单片机的时钟就是MCU内部的谐振电路外加晶体提供的。
STM32外部晶振不起振
https://blog.csdn.net/qq_33559992/article/details/83009134?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522162885171416780366558740%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fall.%2522%257D&request_id=162885171416780366558740&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2allfirst_rank_v2~rank_v29-13-83009134.pc_search_similar&utm_term=%E6%80%8E%E4%B9%88%E5%88%A4%E6%96%AD%E5%8D%95%E7%89%87%E6%9C%BA%E7%9A%84%E6%99%B6%E6%8C%AF%E6%9C%89%E6%B2%A1%E6%9C%89%E8%B5%B7%E6%8C%AF&spm=1018.2226.3001.4187
单片机外部晶振接的是无源晶振，因此必须首先烧写程序进去，配置好相应的寄存器，晶振才会起振。如果没有烧写程序的新单片机（未配置寄存器）则不会起振。
示波器测量晶振、万用表测量晶振的方法
https://blog.csdn.net/weixin_37787043/article/details/92439522?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522162885272216780261931844%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fall.%2522%257D&request_id=162885272216780261931844&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2allfirst_rank_v2~rank_v29-2-92439522.pc_search_similar&utm_term=%E6%99%B6%E6%8C%AF%E7%9A%84%E7%94%B5%E5%8E%8B%E6%80%8E%E6%9C%AB%E6%B5%8B%E9%87%8F&spm=1018.2226.3001.4187
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