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HSE Clock Crystal Circuit

Question asked by wormsley.jeff on Jun 11, 2012
Latest reply on Jun 12, 2012 by John F.
Looking at the STM3210B evaluation board schematic, the 8Mhz crystal has a 1M resistor in parallel across the crystal. 

Looking at the STM3210E evaluation board schematic, the 8Mhz crystal has a 390 resistor between the OSC_OUT pin and the crystal.

Our older boards using STM32F103C8 parts used the former, and a new design with an STM32F103ZE is using the latter, but both seem to work for either CPU.

Can someone tell me what the difference is, and which is recommended for new designs? 

Thanks,
  Jeff.

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