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I am programming an STM32 (manual here). Page 83 has a diagram indicating that the HSE Clock frequency is between 4 and 26 MHz.

The paragraph on HSE clocks starts on page 84, but does not give any information regarding setting the clock to a specific frequency. I have had a look at the RCC registers (starting from page 91) and could find how to turn on/off several clocks, and set various prescalers. I haven't found any register dealing with setting and reading the HSE clock frequency.

How can I read/write the HSE clock frequency?

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You have to supply the clock to the chip with either a crystal/ceramic resonator or other external clock signal.

The 4 to 26 MHz is not generated by the chip itself...

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  • \$\begingroup\$ Yep, that's right. My dev board has an HSE clock of 25MHz. Thanks. \$\endgroup\$
    – Randomblue
    Mar 22, 2012 at 11:47

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