issue about the Clocks Generator

[xiaochenqiang]

I am using the CPU MC9S12XEP100,and using CMOS Compatible External Oscillator,

Question 1:the  Lock bit of the CRGFLG Register can not change to 1,it is always 0，why?the oscillator Circuit and scope as below:

the same program in Many other CPU can change to 1 and work normaly,but individual CPU can not change to 1,why?

Question 2: The CPU can not download the program after change the Oscillator Circuit，why?the changed Circuit and scope as below:

[danielmartynek]

Hi,

The clock must be 1.8V CMOS compatible.

But the amplitude of your clock is over 5V.

Please refer to the below specification,

Table A-1 Absolute Maximum Ratings.

Table A-24 Oscillator Characteristics.

Regards,

Daniel

[xiaochenqiang]

Hi,

Many of the my products using the schematic as the first picture above,and they can work nomaly,why?

some products can not work nomaly after one or two years,I do not know if this is the reason？thank you!

[danielmartynek]

Hi,

It is difficult to say why some MCUs work and others don’t. Is it possible that they are running in Self Clock Mode instead? Indicated by CRGFLG[SCMIF, SCM] bits.

Anyway, the external clock must not exceed the specification given in the RM.

Otherwise, the functional operation is not guaranteed.

Regards,

Daniel

[xiaochenqiang]

The SCM bit is 0,SCMIF bit is 0,

and I test the VDDPLL voltage,it is 3.44V,

now some MCUs can not work nomaly after nearly two years using,The phenomenon of the MCU can not work is running in the car for a period of time crash,

Maybe the MCU inter clock module have bad,resulting in the MCU can not work normaly.

[danielmartynek]

Hi,

VDDPLL supply voltage, nominally 1.8V, is derived from internal voltage regulator.

Please refer to Table A-1 Absolute Maximum Ratings, VDDPLL can be max 2.16V when the device is powered from an external source. Footnote 1 of the table reads “Beyond absolute maximum ratings device might be damaged.”

Regards,

Daniel