MSP430F67761: some questions about accurate clock, MCLK and 5MHz UART

Jerry Kuo

Expert 3855 points

Part Number: MSP430F67761

Tool/software:

Hi team,

My customer is developing MSP430F67761IP FW. They have some questions listed as below. Please help clarify. Thank you.

Customer learned MSP430F67761 cannot provide accurate 25MHz HFXT externally. Customer want to know if they need a more accurate clock, is that possible to feed the Oscillators clock by "P4.3/PM_UCA3CLK/S29"?
if question 1 is yes, then what settings in the software need to set ?

below list another questions about MCLK and 5MHz UART

3. If this MCU clock is DCO structure, What registers should they set to make MCLK run at the highest internal frequency?

4. How to set the eUSCI (UART Mode) to support 5MHz (UART Mode) bit rate?

21 days ago

0 David Schultz 21 days ago

Guru 21965 points

The usual way to get an accurate clock is with a crystal on XT1 as the reference for the FLL. All described in the documentation and example code provided.

0 Dylan OBrien 21 days ago in reply to David Schultz

TI__Genius 14110 points

Hi Jerry,

As David mentions, typically if you want a more accurate clock you'd want to use an external crystal as a reference for the FLL. See the reference code for this in the TI Resource Explorer.

As for which registers to configure for the DCO, again this is covered in the above example. As for customizing your implementation, I recommend taking a look at section 5 of the device family user's guide for descriptions of each register. You can also refer to section 5.19 of the datasheet for the clock frequencies for different DCO settings.

As for configuring the UART, please see this example in the TI Resource Explorer. You'll need to set the input clock and baud rate prescalers shown in section 36.4 of the family user's guide to set the UART clock to 5MHz.

0 Jerry Kuo 21 days ago in reply to Dylan OBrien

TI__Expert 3855 points

Hi David, Dylan,

Thanks for your information. I will let customer check if they need more information.

**Attention** This is a public forum

MSP low-power microcontrollers

MSP low-power microcontroller forum

MSP430F67761: some questions about accurate clock, MCLK and 5MHz UART