Derive an exact timer rate from PLL

[e d]

Posted on May 30, 2017 at 20:46

Hello,

I am working with the STM32L486 chipset and we need to generate an exact 38400Hz timer. Currently we have a 5MHz or 25MHz external clock coming in but the PLL clock tree does not seem to favor getting the exact 38400Hz rate for a timer. Is it possible with the above external clock rates? or if not, any suggestions to get this, including a different rate for external clock source?

Thanks,

ED

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[Tesla DeLorean]

Posted on May 30, 2017 at 21:32

At 12 MHz input clock you can run CPU at 24, 48 or 72 MHz

I believe an input of 4, 8 MHz would also offer these. An input of 24 MHz would provide for multiple additional options ranging from 19.2 thru 76.8 MHz

[e d]

Posted on May 30, 2017 at 23:33

Thanks Clive One! I found a crystal at 19.2MHz available that would also do the job.