Actually this is a basic question I can't answer myself to be honest.

I am using a MCU which requires a HSE:

MCU datasheet application of a HSE

Now, this is for a crystal, but how do I connect a crystal oscillator with the MCU?

The oscillator's datasheet says: LINK

But where do I connect the oscillator's output to the correct PIN on the MCU -> Should it be "OSC_IN" or "OSC_OUT" pin on the MCU like this(?):


  • 3
    \$\begingroup\$ Connect the HSE OSC_OUT to the MCU OSC_IN. Also, depending on the MCU you might have to configure it for an external clock source instead of an MCU controlled crystal oscillator. \$\endgroup\$
    – Janka
    Commented Nov 15, 2021 at 0:20
  • \$\begingroup\$ I see, thats why the "BYPASS clock source" needs to be enabled in the config and the output pin is turned off. Thanks \$\endgroup\$
    – Dakalaom
    Commented Nov 15, 2021 at 0:30

1 Answer 1


Your example shows connection for quartz resonator to MCU. In that case oscillator is inside chip. But your question about external oscillator. Output of external oscillator should be connected to MCU OSC input. And MCU should be set correctly.


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