Hello Pierre,
- It seems if the external crystal is 8Mhz, the PEE mode can not generate core clock with 100MHZ.
From the datasheet we can see the PLL output range is 110MHZ - 240MHZ,

so the range of PLL on Clock configure tool is 220 - 480 , it can't choose 200MHZ.
- You can increase the external crystal, for example 16MHZ:

Hope it helps
Have a great day,
TIC
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------