TMS320F28335: Questions about the system clock and PLL

? ?

Part Number: TMS320F28335

Tool/software:

TI's experts:

Hello!

I am a new user of 28335 and I have been having some problems with the system clock section recently.
If I am using an external oscillator connected to the XCLKIN pin and not using an on-chip oscillator, do I need to write this in code? Because I saw in the 2803 x series chips related instructions are included in the routine, such as SysCtrlRegs. CLKCTL. Bit. XCLKINOFF = 1; // Turn off XCLKIN

Does it need to be written like this in 28335?

The second question is when configuring the frequency division and frequency doubling factor, I want to adjust the frequency division factor to 1. Can I adjust the frequency division factor to 1 only when the PLL is bypassed or turned off?

Thank you!

over 1 year ago

0 Benjamin Collier over 1 year ago

TI__Mastermind 36526 points

Hi,

Our expert on this topic is out of office until next week, please expect a delayed response.

Best Regards,

Ben Collier

0 Matt Kukucka 11 months ago

TI__Genius 13505 points

Hi,

As per the datasheet:

A 3.3-V external oscillator can be directly connected to the XCLKIN pin, but the X2 pin should be left unconnected and the X1 pin tied low. The logic-high level in this case should not exceed VDDIO. Thus, there is no XCLKINOFF bit in F2833x since the XCLKIN and X1/X2 signals are put through an XOR gate.

? ? said:
Can I adjust the frequency division factor to 1 only when the PLL is bypassed or turned off?

Yes, that's correct. Please see section 8.6.1.2 in the datasheet for CLKIN divide options.

Best,

Matt

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TMS320F28335: Questions about the system clock and PLL