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Basic Clock Module+ Block Diagram

eric chung
Prodigy 80 points

The document:  "MSP430x2xx Family User's Guide (Rev. F)" , slau144f.pdf,

on page 5-5 "LFXT1 Oscillator", it says

"Software can disable LFXT1 by setting OSCOFF, if LFXT1CLK does not source SMCLK or MCLK"

but on page 5-3  "Basic Clock Module+ Block Diagram",

this diagram  shows LFXT1 can disable by clearing OSCOFF

http://img143.imageshack.us/img143/3443/8888zu.png

is it a mistake?

 

 

 

 

  • 0
    Guru 227245 points

    eric chung said:
    s it a mistake?

    Well, one could say so.

    The OSCOFF register marker in the diagram does not contain any polarity info. it 'influences' the input driver and the oscillator, but this does not necessarily mean that a '1' value in the register means 'enable'.

    One cold draw an inverting circle on the driver, but for the oscillator blackbox, the signal polarity has no meaning in this drawing, so I guess that for the driver, it was left to the register description too.

     

    In any case, setting OSCOFF bit will disable the (LF)XT1. That's why the register bit is named OSCOFF. it's what it does when set.

    Same applies to XT2OFF

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