i.MIMXRT1021CAG4A external OSC

[vlad95vlad]

Hello, i have 25 MHz external clock in my custom board with i.MIMXRT1021CAG4A. But MCU Expresso IDE doesn't allow to set this value. Should i use 24 MHz external clock only? Also there is Table 13-5 (System Clock Frequency Values) on page 850 in i.MX RT1020 Processor Reference Manual. Are these maximum frequency values available only for MIMXRT1021DAG5A? Can i.MIMXRT1021CAG4A reach it too?

Regards.

[Yuri · Accepted solution]

Hello,

According to section 4 (Clocks) of the Hardware Development Guide for the MIMXRT1020:
The 32.768 kHz and 24 MHz oscillators can’t be replaced with crystal with other frequency.

https://www.nxp.com/webapp/Download?colCode=MIMXRT1020HDUG

Let me remind, such interfaces as Ethernet and USB are frequency sensible.

The Table 13-5 is correct for both consumer and industrial variants of i.MX RT 1020.

Regards,
Yuri.

[mjbcswitzerland]

Hi

The internal PLLs in the 1021 are designed around a 24.000MHz reference.

A 25MHz crystal is not foreseen and so should generally not be used unless you are not working with any PLLs (that is from 25MHz directly without using HSUSB or Ethernet, or other peripherals that depend on the exact PLL outputs)  and you are developing in a non SDK environment.

Regards

Mark
[uTasker project developer for Kinetis and i.MX RT]
Contact me by personal message or on the uTasker web site to discuss professional training, solutions to problems or rapid product development requirements

For professionals searching for faster, problem-free Kinetis and i.MX RT 10xx developments the uTasker project holds the key: https://www.utasker.com/iMX/RT1020 .html