Clock using internal 48M-IRC oscillator

smathad — Thu, 30 Jan 2020 13:49:26 GMT

Hello all,

We are working on K24 and we are switching from 8MHz crystal to the IRC48M internal oscillator for our legacy systems.

We have observed that the controller operates in FEI mode on RESET and moves into PEE mode.

It transitions from FEI -> FBE -> PBE -> PEE mode.

While we are able to generate the same core, bus and flash frequencies in FEI and PEE mode, we are unable to generate similar frequency(generating higher frequency) as the legacy system in FBE and PBE mode using OUTDIV.

My question is, since we are entering FBE and PBE only to transition to PEE is it okay to have higher frequencies than the legacy systems?

Please find the table to see the frequencies:

Modes	8MHz crystal output	48MIRC oscillator output
FBE and PBE modes	8 MHz - Core 4 MHz - Bus 1.6MHz - Flash 1.6Mhz - Flex	48 MHz - Core 24 MHz - Bus 9.6 MHz - Flash 9.6MHz - Flash

Modes

8MHz crystal output

48MIRC oscillator output

FBE and PBE modes

8 MHz - Core

4 MHz - Bus

1.6MHz - Flash

1.6Mhz - Flex

48 MHz - Core

24 MHz - Bus

9.6 MHz - Flash

9.6MHz - Flash

Re: Clock using internal 48M-IRC oscillator

mjbcswitzerland — Fri, 31 Jan 2020 14:35:48 GMT

Hi Sachin

As long as the clocks are within specification during the transition there is no problem.

See https://www.utasker.com/kinetis/MCG.html for practical MCG guide.

Regards

Mark
[uTasker project developer for Kinetis and i.MX RT]

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Clock using internal 48M-IRC oscillator

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