i.MX6 Solo CPU Reset timing incorrect

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i.MX6 Solo CPU Reset timing incorrect

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vincentchou
Contributor IV

Hi!  Support,

We have one board with two different CPU versions.  One is i.MX6 Solo and the other is i.MX6 DL.  The CPU reset wiring is completely the same as it is on SabreSD board.  Now we use the CPU reset key to power off board as our production version.  Unfortunately after we ship our products to the field, we found out the Solo version demonstrate different characteristics.  Based on the CPU datasheet, supposedly the board needs to be shut off after 5 seconds.  However, we do find a percentage of these boards can be shut off within a second or two.  However, DL version does follow the datasheet to shut off after 5 seconds.  Is this a CPU problem?  

Vincent

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igorpadykov
NXP Employee
NXP Employee

Hi Vincent

this may be caused by improper operation of 32.768 kHz oscillator,

in such case processor uses internal ring 40 kHz oscillator. The tolerance is ± 50%.

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Best regards
igor
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vincentchou
Contributor IV

Hi!  Igor,

If we use an external RTC IC circuitry and leave RTC_XTALI open, is it going to affect the reset time?  Can we keep the same oscillator input in our design but does not define SNVS RTC in the device tree in the next layout?  Also, is it possible for us to modify the firmware in to let CPU refers to a different clock source?  We appreciate your suggestions very much.

Vincent

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igorpadykov
NXP Employee
NXP Employee

Hi Vincent

leaving RTC_XTALI open will cause processor to use internal RTC oscillator

with implications given above.

Best regards
igor

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vincentchou
Contributor IV

We have a few cases which has immediate reset effect on touching the reset button.  Do you think this is caused by the same issue.  

Also, if we did not put oscillator on RTC_XTALI, will be present a coherent reset timing even though it is not 5 seconds.  For instance, if we observe a 3 second reset time on pushing reset button, will it be 3 second still next time?

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