• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 2 answers
  • Subscribers 80 subscribers
  • Views 941 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

MSP430F2252: LFXT1 Oscillator Allowance in HF Mode

Stuart Baker
Genius 10670 points
Part Number: MSP430F2252


We have found what appears to be a discrepancy in the datasheet of this device.  When I look at the published OAHF value for 4 MHz, I see 800-ohms but this does not match the curves shown in Figure 18.  The other values I see for OAHF match but the 4MHz value is an order of magnitude different.

Please explain the discrepancy and which number is correct.

Thanks,

Stuart

  • 0
    TI__Mastermind 49692 points
    Hello Stuart,

    Looking at the graph, the plotted data appears slightly lower than it should based on the data in the Table. Also, the individual plots seem to be shifted by LFXT1Sx + 1. For example, the plot for LFXT1Sx = 1 appears to cross 2700 Ohms at 1MHz, but according to the Table, this should be the plot for LFXT1Sx = 0. I'll submit a bug internally and ask for clarification. I'm not sure how long it will be until I get a response, but I'll keep you updated when I hear something back.

    Regards,

    James
  • 0 in reply to James Evans
    TI__Mastermind 49692 points
    Hello Stuart,

    Thanks for your patience here. I've confirmed that the curves in Figure 18 are correct and the values in the Table are incorrect. The Table should have values for LFXT1Sx = 1, 2, and 3 rather than 0, 1, and 2. We'll be updating the datasheet soon.

    I hope this helps!

    Regards,

    James
  • 0 in reply to James Evans
    Prodigy 20 points
    Hi James,

    When I review the documentation for MSP430F2252 I see the valid settings for the LFXT1Sx bits when using the MSP HF oscillator (BCSCTL3.LFXT1Sx register when XTS=1) are 0 (00b), 1 (01b), and 2 (10b). LFXT1Sx=3 appears to be reserved for an external digital clock source where the MSP430 oscillator circuitry is not used and therefore the OAHF of that circuitry is not important. The valid setting for LFXT1Sx can be reviewed by referencing SLAU144J section 5.2.3 & page 5.3.4. The datasheet (SLAS504G) table containing the OAHF specifications also shows LFXT1Sx=3 as reserved for a digital clock input “FLFXT1,HF,logic”.

    My follow-up question to this inquiry is how should I interpret Figure 18 (and Figure 19) in SLAS504G with respect to the valid assignments for BCSCTL3.LFXT1Sx when using a resonator/crystal? BCSCTL3.LFXT1Sx=3 is not valid when using the MSP internal oscillator circuitry but each figure has LFXT1Sx=3 and is missing LFXT1Sx=0. I wonder if the LFXT1Sx values shown in Figure 18 (Figure 19) are not in error and maybe need to be decremented by one?

    Thank you for your help.

    JamesW
  • 0 in reply to JamesW
    TI__Mastermind 49692 points
    Hi JamesW,

    Thanks for your detailed reply. I see exactly what you're saying, and I agree with your interpretation. Let me get confirmation and get back to you.

    Regards,

    JamesE
  • 0 in reply to James Evans
    TI__Mastermind 49692 points
    Hi JamesW,

    I'm still waiting on feedback from our team, and due to international holidays, it could be a week or two before I can get confirmation. As soon as I hear anything, I'll let you know. Again, thanks for your patience.

    Regards,

    JamesE
  • 0 in reply to James Evans
    TI__Mastermind 49692 points
    Hi JamesW,

    Thanks for your patience. I've received confirmation that Figures 18 and 19 should be updated to 0/1/2 and the values for OAHF in the table are correct. This will be updated in a future version.

    Regards,

    James
  • 0 in reply to James Evans
    Prodigy 20 points
    Hi James,

    Thank you for the resolution.

    JamesW

**Attention** This is a public forum