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MCG configuration in mqx for k65f180m for using internal reference clock

Question asked by annamol alex on Dec 30, 2015
Latest reply on Jan 1, 2016 by Mark Butcher

Hi,

I am trying to configure the internal reference clock for K65F180m in mqx. I have read the utasker documentation on MCG modes and have gone through the reference manual. I have certain doubts regarding MCG. It would be of great help if anyone can clarify them

  • For using the IRC, I could find only these configurations. Is there anything more missing (the values configured in registers are mentioned in barckets)
    • MCG_C1-> CLKS(1) ,IREFS (1), IRCLKEN(1)
    • MCG_C7 ->OSCSEL(2)
    • OSC_CR ->ERCLKEN (0)
    • MCG_S ->IREFST(1),CLKST(1),IRCST(1)
    • SIM_SOPT2 ->PLLFLLSEL (3), SIM_SOPT2_USBSRC_MASK
    • SIM_SCGC4 ->SIM_SCGC4_USBOTG_MASK;

    • USB0_CLK_RECOVER_IRC_EN ->USB_CLK_RECOVER_IRC_EN_REG_EN_MASK
    •   USB0_CLK_RECOVER_CTRL  ->USB_CLK_RECOVER_CTRL_CLOCK_RECOVER_EN_MASK
  • When i add the above configurations in my project, the debugging session stops. It might be because of the mismatch in clock. But I read in a post that Jlink OpenSDA won't have issue with lower clock. but mine is openSDA.
  • In mqx project, i made the following changes in bsp_cm.c file. i am not sure if this is correct or not
    • for making that change i commented off the OSC_CR and mode changing sections in pe_initialize_hardware

 

void __pe_initialize_hardware(void)

{

    /* OSC Configure */

    OSC_CR |= ~OSC_CR_ERCLKEN_MASK;

//    /* after enter FEI Mode */

//    Cpu_SetMCGModeFBE(0);

//    Cpu_SetMCGModePBE(0);

//    Cpu_SetMCGModePEE(0);

}

 

  • Is it possible to completely remove the external crystal and power up the board. In all the initialization sections, I could see the external reference clock being used in code. Can we do it using the 32KHz and 4MHz crystals available?
  • Can we generate the code to use internal reference clock alone for the K65  MCU using processor expert? Is there any document available for the same
  • In the MCG documentation, we  have MCG in FEI mode when it comes out of reset, Is this reset referring to a full system reset? Does this mean that an external crystal is needed for the MCU operation. Is crystal less operation possible, any document available for the same.

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