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MCF51QE high internal reference clock

Question asked by Johan Bolin on Oct 3, 2016
Latest reply on Oct 3, 2016 by TomE

Hi,

I recently started working with a product incorporating the MCF51QE128. According to the data sheet the typical value for the internal reference clock is 32.768 kHz. However, when I try to verify this by measuring on GPIO toggled by a TPM interrupt the derived clock appears to be 38.4 kHz. The trim value is loaded from flash address 0x03FF (0x0061). Other settings are:

 

DRS = 00

DMX32 = 0

BDIV = 0

 

The debugger outputs "Bus Freq = 9837KHz" which also points to 38.4 kHz reference clock.

 

Is the trim value wrong? Or am I missing something else?

 

Best Regards,

Johan

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