It has to configure some PLLs so everything on the chip has clocks to work with.

它必须配置一些 PLL，以便芯片上的所有东西都可以使用时钟。

Is this because it initializes PLLs, and these PLLs need some time to lock every time you reset? And this seems to take a different amount of time every time it does that.

是不是因为它初始化了PLL，每次reset的时候这些PLL都需要一些时间来lock？每次这样做似乎都需要不同的时间。