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TMS320F280041C: Oscillator setup

Pavlin Stoyanoff
Expert 1715 points

Part Number: TMS320F280041C

Tool/software:

Greetings! I am using this chip for a very first time and it seems I have made a mistake in the oscillator setup. I have 10MHz external crystal and I am using this settings -> 

 // PLLSYSCLK = 10MHz (XTAL_OSC) * 20 (IMULT) * 1 (FMULT) / 2 (PLLCLK_BY_2)
  SysCtl_setClock(SYSCTL_OSCSRC_XTAL |
                  SYSCTL_IMULT(20) |
                  SYSCTL_FMULT_NONE |
                  SYSCTL_SYSDIV(2) |
                  SYSCTL_PLL_ENABLE);

It seems these are incorrect settings and I have problems with the SCI module. If I try to enter this settings in an example like sci_ex2_interrupts the F280041C can`t init. 

Can you tell me in which datasheet I can find info about these settings and in what range they can vary? Or what mistake I have done?

Thanks!

  • 0
    TI__Mastermind 40540 points

    Hi Pavlin,

    The clock specs can be found in section 7.9.3.2.2 of the F28004x datasheet.  I do not see anything wrong with the multiplier and clock settings.  A 10MHz XTAL with a 20 multiplier produces a VCO of 200MHz, which is within the bounds of the 120-400MHz VCO range for the PLL.  This is further divided by 2 (SYSDIV) to produce the 100MHz SYSCLK which is the spec for F28004x.

    There is a #define parameter DEVICE_OSCSRC_FREQ.  Make sure to change this to 10000000U, to get the proper SYSCLK.  The default in the example is 20000000U.  If this is not modified then SYSCLK will be set at 200MHz, which the device cannot support.

    Regards,

    Joseph