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Original question:

MSP430I2021: Questions about external resistor tolerance and calibration, different clock frequency and unique memory id...

MSP430I2041: About using a 16MHz external oscillator for MSP430I20xx

O.H
Genius 5350 points
Part Number: MSP430I2041

(Sorry. I made a mistake in the "Part Number" when I posted this article, and used I2021. The correct part number is I2041.)

Hi experts,

My customer is planning to use a 16MHz external oscillator with MSP430I2041. I am referring to the original question, but let me check just to be sure about the case of MSP430I2041.

Q1: When using a 16MHz external oscillator, the SD24 is supplied with a 1MHz clock. But the accuracy at 1MHz is not described in the datasheet, so they have to make sure they meet the requirements themselves. Is this correct?

Q2: When using a 16MHz external oscillator, is there any other possible effect on the SD24?
For example, effects on serial communication such as UART baud rate, etc. I understand that there is not expected to be any long term impact on the device.

Referring to the contents of the datasheet and user's guide, we plan to tell customers that the recommended basic premise is to use 16.834MHz for the external oscillator.

Best regards,
O.H

  • +1
    TI__Mastermind 49692 points

    Hello,

    O.H said:
    (Sorry. I made a mistake in the "Part Number" when I posted this article, and used I2021. The correct part number is I2041.)

    No problem. I updated the thread title.

    O.H said:
    Q1: When using a 16MHz external oscillator, the SD24 is supplied with a 1MHz clock. But the accuracy at 1MHz is not described in the datasheet, so they have to make sure they meet the requirements themselves. Is this correct?

    Correct.

    O.H said:
    Q2: When using a 16MHz external oscillator, is there any other possible effect on the SD24?
    For example, effects on serial communication such as UART baud rate, etc. I understand that there is not expected to be any long term impact on the device.

    The datasheet includes guidance on clock frequencies for each module. For UART mode, the eUSCI input clock frequency can be up to Fsystem, which has a max frequency of 16.384 MHz but can support lower frequencies such as 16 MHz. As long as they understand the SD24 ADC performance will be impacted and that impact is acceptable for them, then other modules of the i20xx should function correctly at 16 MHz. Have them double-check the datasheet to confirm.

  • 0 in reply to James Evans
    Genius 5350 points

    Hello James Evans,

    Thank you for your reply.

    I understand your answer, but I would like to confirm one point.

    Q3:"Recommended Settings for Typical Crystals and Baud Rates" in "MSP430i2xx Family User's Guide (Rev. A)" does not list error rates when using 16.384MHz. Where should I refer to?

    I think the feature of this device is that it does not need an external crystal and the DCO outputs 16.384MHz. However, I was curious because the user's guide seemed to assume that a 16MHz system was input.

    Best regards,
    O.H

  • 0 in reply to O.H
    TI__Mastermind 49692 points
    O.H said:
    Q3:"Recommended Settings for Typical Crystals and Baud Rates" in "MSP430i2xx Family User's Guide (Rev. A)" does not list error rates when using 16.384MHz. Where should I refer to?

    That's correct. Since 16.384 MHz isn't included, you'll have to calculate the error rates manually. The previous section in the user's guide describes how to perform the calculation. An easier approach may be to set up the internal DCO to run at 16.384 MHz and measure the error rate based on the actual UART communication.

    O.H said:
    I think the feature of this device is that it does not need an external crystal and the DCO outputs 16.384MHz. However, I was curious because the user's guide seemed to assume that a 16MHz system was input.

    This table is used across several device families and is generic. You're correct that this device does not need an external crystal and features an internal DCO.

  • 0 in reply to James Evans
    Genius 5350 points

    Hello,

    James Evans said:
    That's correct. Since 16.384 MHz isn't included, you'll have to calculate the error rates manually. The previous section in the user's guide describes how to perform the calculation. An easier approach may be to set up the internal DCO to run at 16.384 MHz and measure the error rate based on the actual UART communication.

    Sorry. It had slipped my mind that I should calculate it manually...

    I understood. Thank you for your kind support!!

    Best regards,
    O.H

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