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Stuck at Self Clock Mode

Question asked by Ville Vieri on Aug 18, 2017
Latest reply on Aug 21, 2017 by Ville Vieri

I have 9S12C64CFAE processor (0M66G mask) with Pierce oscillator setup running at 8MHz. For some reason the chip is still running on SCM although the crystal oscillator has nice and full-swing waveforms and starts very fast after the supply voltages are present.

 

EXTAL signalXTAL signal

I used BDM to get some information on the register contents and the status register 0x0037 (CRGFLG) shows 0x63 that means that the SCM is active.

I have fundamental 8MHz crystal with 22pF load capacitors (recommended by the crystal manufacturer) and 10M resistor in parallel with the crystal.

As far as I understood, the SCM bit is set purely by hardware and it is not software dependent. Or am I wrong?

So, without any firmware inside the chip should use the external clock (at least when looking at reset values of registers) and not to go into SCM?

Have programmed also the S12SerMon2r1 in using the BDM programmer, but it does not make situation any different...

I have also tried to wire the crystal directly to the chip with associated components to minimize the signal lengths and stray capacitances but the result is still the same.

I really appreciate any help.

Regards, Ville

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