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Original question:

TMS320F280049: Question about Crystal Oscillator start-up time

TMS320F28374D: Question about Crystal Oscillator start-up time

Julia Li
Expert 4755 points

Part Number: TMS320F28374D

Hi Champ,

 

I have checked below E2E case and I still want to confirm more information about start-up time. 

https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/993272/tms320f280049-question-about-crystal-oscillator-start-up-time/3670491?tisearch=e2e-sitesearch&keymatch=start-up%20time%20AND%20crystal#

In the datasheet, the typical value of start-up time is 2ms. In the above E2E discussion, an expert replied that it depends on the crystal oscillator used by the customer. However, I took a look at our bit-field example code F2837xD_SysCtrl.c file there is a 300NOPS delay. Is this delay set for start-up time? Have you confirmed that 300 NOPs are sufficient? 

image.png

 

Thanks!

 

Best Regards,

Julia

  • +1
    TI__Genius 15440 points

    Hello,

    That 300 SYSCLK cycle delay relates to "SYSTEM: Multiple Successive Writes to CLKSRCCTL1 Can Cause a System Hang" in the F2837xD Silicon Errata.

    Assuming SYSCLK = 10MHz, that means 300 cycle delay would be ~0.03ms, which is not sufficient. 

    Please see SysCtl_pollCpuTimer() in sysctl.c of the F2837xD driverlib to see how powering up XTAL is implemented.

    Best,

    Matt