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MSP430F5529 : How to calibrate DCO using DCORSEL DCO and MOD register values

Other Parts Discussed in Thread: MSP430F5529

Hello,

I am using the MSP430F5529 LaunchPad for some basic stuff.

In the Student Guide that comes for the MSP430 series of controllers, it specifies a method of setting up the DCO for configuring the SMCLK ACLK etc. 

It basically tells us to use the DCORSEL to select the range of freq (withing which the required freq lies), fix a value for the DCO tap by diving the DCORSEL "range" into 32 divisions and selecting the freq which you want.

But the part I dont understand is the RANGE that a particular value of DCORSEL . All I have is this graph which cannot be used to get the exact values (or am I missing something?)

The ranges given in the table is also confusing:

I am ideally looking for a X and a Y for a particular value of DCORSEL which I would use in a formula (Y-X)/32 to get the value of DCO.

I need to know the ranges that I would get on selecting a DCORSEL value

  • You definitely shall read User's Guide, DCO chapter. [edit] Better check whole "Unified Clock System (UCS)" part. If you still have questions - do not hesitate to ask here.

  • The DCO is implemented with a simple RC oscillator, where DCORSEL and DCO select different values of R and C.

    However, it would be very hard (i.e., expensive) to have accurate resistors or capacitors integrated in a chip, so the F5529 does not even try. There are no exact values; e.g., selecting RSEL=1 and DCO=0 would result in a frequency anywhere between 150 kHz and 360 kHz.

    To get an accurate frequency out of the DCO, you have to use the FLL to stabilize it to a multiple of some more accurate reference clock.
  • It has been soo helpful. Thanks a lot!!!! Seriously, a very good answer, very very useful ....................
  • Nicol��s Salguero said:
    It has been soo helpful. Thanks a lot!!!! Seriously, a very good answer, very very useful ....................

    You are not satisfied that I did not read documentation for you and provide "ready to use" solution in edible form? Please tell me one reason why should I do that - if you can find answer yourself, by reading documentation.

    You said:

    >>All I have is this graph which cannot be used to get the exact values (or am I missing something?)

    I answred that you missed to read User'sGuide where is information you were looking for.

  • I am sorry about that. I was just starting with my project and didn't have any clue about how to manage all this information.
    Thanks for your contribution.

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