PLL1 possible "users"

[rafaelbastos]

Hi dears, I´m learning regarding LPC176X/5X and, on topic 4.6 from UM10360, I have understood the PLL1 is specific to drive USB subsystem.

Other wise, on table 36 from sub topic 4.6.9, there is a statement that highlighted values are the ones allowed for using PLL1 with USB.

So is correct my understanding that the PLL1 could be used to drive other subsystem or with other functions ? If so witch ones ?

Best regards,

Rafael

[jeremyzhou]

Hi Rafael Bastos,

Thank you for your interest in NXP Semiconductor products and 

for the opportunity to serve you.

The PLL1 (USB PLL1) is used to provide a fixed 48 MHz clock only to the USB Module as the Fig1 demonstrates,

Fig 1

Have a great day.

TIC

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

[rafaelbastos]

Hi Jeremyzhou, first of all thanks for your attention. As I told I´m studying the LPC176X/5X family, and the main proposal is to teach people about that. So, in my point of view, details are very important in that case.

I still having just one doubt, on the document I have referenced above (UM10360) there is a comment, on Tables 36 and 37 from Chapter 4, informing that "highlighted values are allowed for using PLL1 with USB". What would happens if I use other values? Would I just get wrong frequency from PLL1?

Sorry for boring you, but I really like to undestand the low level details.

Thanks once more,

Rafael.@

[jeremyzhou]

Hi Rafael Bastos,

Thanks for your value.

I think the PSELS1 bits should be invisible to the users, as only P=2 yield FCCO in the allowed range.

The highlight values of MSEL1 bits is refer to FOSC = 24 MHz, 16 MHz or 12 MHz which are recommended frequency of the FOSC.

Hope this is clear.

Have a great day.

TIC

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------