Unexpected behavior in kl25z TPM.

Mockingbird · ‎03-21-2018

I am programming a kl25z on a Freescale FRDM-KL25Z board using assembly language. My IDE is CodeWarrior 10.7. My program is a simple LED-blink program. I use the TPM output compare interrupt to schedule the blinks.

The program works correctly when I connect TPM to the FLL. The program fails to work when I connect TPM to MCGIRCLK. The only differences between the two versions of the program are in SIM_SOPT2 TPMSRC (which selects the TPM clock) and in TPM0_SC PS (the TPM clock prescaler).

When I write corresponding C-programs with help of the Processor Expert, the C- program works both when TPM is connected to FLL and when TPM is connected to MCGIRCLK.

Why won't my assembly-language program work with TPM connected to MCGIRCLK?

mjbcswitzerland · ‎03-22-2018

Timothy

Load the code that works, let if run, then pause it and do a screen shot of all relevant registers.

Then load your code and do the same.

You should be able to see a difference in a register somewhere showing what is missing to get it working the same way.

Regards

Mark

View solution in original post

mjbcswitzerland · ‎03-21-2018

Hi Timothy

You probably need to enable the MCGIRCLK clock gate with IRCLKEN in register MCG_C1.
To get 4MHz MCGIRCLK remove its divider to get 4MHz clock (MCG_S = 0) and select 4MHz instead of 32kHz with IRCS in register MCG_C2.

Regards

Mark

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Mockingbird · ‎03-22-2018

The code I attached shows that IRCLKEN is already set. The debugger confirms this.

mjbcswitzerland · ‎03-22-2018

Timothy

Load the code that works, let if run, then pause it and do a screen shot of all relevant registers.

Then load your code and do the same.

You should be able to see a difference in a register somewhere showing what is missing to get it working the same way.

Regards

Mark

Mockingbird · ‎03-22-2018

Thanks, that helped. It turns out the instruction to set IRCLKEN wasn't written correctly; I wasn't taking proper account of the little-endian architecture.