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Support for high frequency crystals on LFXT1 for value line MSP430G2231

John Wright
Intellectual 330 points
Other Parts Discussed in Thread: MSP430G2231

I would like to know if the LFXT1 input of the MSP430G2231 supports either/both higher frequency external crystals or logic level high frequency input at the LF xtal input.

This is useful for accurate high resolution timing of events as the DCO is not frequency locked and the 32768HZ doesn't provide much timing resolution.

It would be good if the data sheet for the MSP430G2231 had a table describing the high frequency modes of the LFXT1 much as in the MSP430F21x2 data sheet (slas578g.pdf).

See page 36 (crystal oscillator,LFXT1, high frequency modes) of the MSP430F21x2 data sheet for a sample of what I'd like to see in the MSP430G2231 data sheet.

Note, the first page of the MSP430G2x31 data sheet (slas694b.pdf) has "External digital clock source" listed, but I couldn't find any information inside the slas694b.pdf document as far as drive levels (again see the MSP430F21x2 data sheet page 36, "LFXT1 oscillator logic level square wave input frequency, HF mode").

While the high frequency crystal capability may be in the MSP430G2231 part currently, if the capability is not listed in the data sheet it could be removed in a future part redesign.

However, I'm pleased with the launchpad hardware TI supplies, it's small enough to build into a prototype product but still has good access to all pins and the parts themselves are at a good price.

 

 

 

 

 

 

 

  • 0
    TI__Genius 17802 points

    Hi John,

    thanks for your keen observation. Unfortunately, the current G2 devices cannot operate the XT1 in high frequency mode. Therefore the datasheet only lists the LFXT1 specs for these devices.

    Nonetheless, the DCO is still available for HF operations. If higher frequency (8/12/16MHz) calibration constants are required,  you can use the Elprotronic  SW to calibrate and program the DCO constants into the device's info memory.

    Regards,

    Dung

  • 0 in reply to Dung Dang
    Intellectual 330 points

    Dung,

    Thank you for your timely response.

    What does the "External Digital Clock Source" imply on the first page of the data sheet for the MSP430G2231 (slas694b.pdf)?

    Does this mean the MSP430G2231 can be clocked externally by a high frequency clock applied to the LFX1 terminal (XIN)?

    Perhaps it refers to the clock output signal (ACLK) available at one of the pins?

    Judging from the value line family data sheet, the high frequency crystal support will eventually be in some of the future value line parts.

    However, while I'd rather have the high stability and accuracy of an external crystal, I believe I can work with the DCO. 

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