I.MX6 MMDC 32Khz refresh clock

[rostyslavkhudol]

Hi all,

I'm struggling to find which 32KHz clock is used by MMDC to perform a periodic auto refresh (ch.

46.4.8)? Is it coming from XTALOSC? It seems to be quite unstable.

[igorpadykov]

Hi Rostyslav

you are right, for that reason recommended to use precision 32.768 kHz

oscillator as stated in Table 2-7. Oscillator and clock recommendations

i.MX6 System Development User’s Guide

https://www.nxp.com/docs/en/user-guide/IMX6DQ6SDLHDG.pdf

Best regards
igor
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[attilasukosd]

As a feedback to NXP, I feel like this could be highlighted a lot more in the design guidelines, hardware design checklist, etc.

We've spent a lot of time debugging undefined behaviour with RAM, watchdog, USB, CEC etc on our custom designed board, only to realize that all of it was due to the inaccuracy of the internal 32kHz clock, which at certain temperatures fluctuated between 14-100kHz.

I'd go as far as to put it in the hardware design checklist explicitly that an external 32kHz clock is a requirement for proper function.