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TMS320C5515 CLKIN & 32kHz crystal

Victor Vanderberg
Prodigy 35 points
Other Parts Discussed in Thread: TMS320C5515

In my application I need to have the option to clock the TMS320C5515 from both CLKIN @ 12MHz & via 32kHz crystal. 

In low power mode I'd like to set CLK_SEL =0, CLKIN=0, and use the 32kHz with PLL to achieve 100MHz system clock.

In synchronous mode I'd like to set CLK_SEL=1, CLKIN=12 MHz oscillator.  

I'd like to control CLK_SEL via an external uC. The design currently allows the uC to power on/off the TMS320C5515.  I also realize that I can't change the mode without a POR.  

I have two questions: 1) does this sound feasible?  2) I'd like to still use the PLL when using the 12MHz oscillator.  Since 12MHz is much higher that the PLLIN requirements does this mean that I need to divide down the reference clock in oroder to use the internal PLL to go back to 100MHz? 

Thoughts would be appreciated.  

Victor 

  • 0
    TI__Genius 14965 points

    Hi,

    Internally, CPU checks CLK_SEL status only when POR happens. You can control CLK_SEL by an external uC and make sure set CLK_SEL before RESET applied.

    For 12MHz PLLIN, you also configure PLL divider correctly to set VCO in the operating frequency.

    Regards,

    Hyun