RT1052 New Board Clock Issue

[RustyWires]

I have a new custom board running an RT052 with a 24MHz TCXO instead of crystal. Debugger connects, loads code, and starts fine.

TCXO clock runs to XTALI with XTALO floating per HRM 15.4.2.

Programs hangs in CLOCK_InitExternalClock() at the following line:

while ((CCM_ANALOG->MISC0 & CCM_ANALOG_MISC0_OSC_XTALOK_MASK) == 0UL)

so it looks like it's not seeing the 24MHz clock.

The scope shows a clean 24MHz clock as close to the XTALI pin as I can measure.

Is there anything different I need to do to run the oscillator instead of a crystal? 

[jeremyzhou · Accepted solution]

Hi,
Thank you for your interest in NXP Semiconductor products and for the opportunity to serve you.
To provide the fastest possible support, I'd highly recommend you check the hardware by following the below tip.

jeremyzhou_0-1650349424641.png

Have a great day,
TIC

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[RustyWires]

Update for others with the same issue:

The datasheet and Hardware reference manual conflict on how to connect an external 24MHz clock source.

I had connected the TCXO per the HRM option 2 (clock to XTALI, XTALO floating). I was able to work around this by commenting out a couple lines in BOARD_BootClockRUN():

//CLOCK_InitExternalClk(0);
//CLOCK_SwitchOsc(kCLOCK_XtalOsc);

This allowed me to run the internal 24MHz RC oscillator

For reference:

Datasheet says Clock must connect to XTALO and connect XTALI to GND with an 18pf cap.

HRM:

15.4.2 Bypass Configuration (24 MHz)
If it is desired to drive the chip with an external clock source, then the 24 MHz oscillator
could be driven in one of three configurations using a nominal 1.1V source.
1. A single ended external clock source can be used to overdrive the output of the
amplifier (XTALO). Since the oscillation sensing amplifier is differential, the
Chapter 15 Crystal Oscillator (XTALOSC)
i.MX RT1050 Processor Reference Manual, Rev. 4, 12/2019
NXP Semiconductors 1183
XTALI pin should be externally floating and capacitively loaded. The combination
of the internal biasing resistor and the external capacitor will filter the signal applied
to the XTALO pin and develop a rough reference for the sensing amplifier to
compare to.
2. A single ended external clock source can be used to drive XTALI. In this
configuration, XTALO should be left externally floating.
3. A differential external clock source can be used to drive both XTALI and XTALO.
Generally, configuration 2 is anticipated to be the most used configuration, but all three
configurations may be utilized.

[RustyWires]

Thanks for the reply.

I see where the datasheet requires driving XTALO and adding 18pF to ground on XTALI.

When designing this, I used the 1050/1060 Hardware Development Guide which referred me to the Hardware Reference Manual. The HRM says there are three options for this connection, but the preferred one is to connect the external clock source to XTALI and leave XTALO floating.

My TCXO is connected to XTALI with XTALO floating as recommended by the HRM. Is there a way to make this work or is the HRM incorrect?

[jeremyzhou]

Hi, Thanks for your reply. 1) My TCXO is connected to XTALI with XTALO floating as recommended by the HRM. Is there a way to make this work or is the HRM incorrect? -- Firstly, I'd like to suggest you try to follow my previous advice to modify the hardware, next, I'm not sure whether the HRM is right or not, plus, it doesn't illustrate any specific requirement about the single-ended external clock source. Have a great day, TIC ------------------------------------------------------------------------------- Note: - If this post answers your question, please click the "Mark Correct" button. Thank you! - We are following threads for 7 weeks after the last post, later replies are ignored Please open a new thread and refer to the closed one, if you have a related question at a later point in time. -------------------------------------------------------------------------------