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If adjusting UCS why increasing Vcore?

Bob Marley
Intellectual 310 points
Other Parts Discussed in Thread: MSP430F5529

Hello everybody!

I  attached the TI source code MSP430F552x_UCS_10.c int o the code of a project on which I am involved at the moment. So far everything works well and I do understand how to deal with UCS now. ... By the way: I am using a MSP430F5529.

But there is just one point I would like to understand a little bit more, just for interest.

 

As far as I do understand  the mentioned TI source code Vcore needs to be increased for getting a higher frequency of the core itself.

So it seems to me that there is a system next to a other which is for managing the frequencies within the uC.

 

When do I need to increase Vcore exactly?

What makes the difference between changing Vcore settings (relating to frequencies of clock) to adjusting UCS?

 

- I suppose that I always have to change Vcore if I want to get a higher clock frequency by UCS. Is this right?

Thank you very much in advance!

 

 

  • 0
    Guru 227245 points

    The CPU core does not know which MCLK frequency you're applying to it. In theory, any frequency can be clocked into the core at any time. Maybe from an external clock source, maybe because your cod eis changing the MCLK source or changing the DCO configuration or just the dclock ivider.
    If you don't care for power consumption, you can jsut set VCore to the the maximum and you're on the safe side.
    But if you care, then you have the option (and neccessity) to adjust VCore matching the frequency range you intend to operate the CPU with. This saves a lot of power. At the cost of some coding overhead - including raising VCore again if you intend to speed the CPU up.

    Bob Marley said:
    I suppose that I always have to change Vcore if I want to get a higher clock frequency by UCS. Is this right?

    No. Only if you want to use these higher frequencies as MCLK. If MCLK is still low, you canraise ACLK and SMCLK to the maximum wihtout any need to change VCore.

    VCore is only for the CPU core (and flash/ram). And this closed system gets MCLK. It doe snot know where MCLK comes from or how fast it is. If it is too fast for the current VCore (or too fast for any), the CPU will crash. It's your hob to esnure that there is never an MCLK signal that is faster than the current VCore allows (and VCore doesn't change immediately with changing the VCore setting. The voltage regulator needs some time to stuff the external capacitors - this is why there is a SVS module that gives you notice.

  • 0 in reply to Jens-Michael Gross
    Intellectual 310 points

    Thanks Jens-Michael Gross for your immediate answer!!

    Have a nice time!

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