MSPM0G3507: DMA writes to UART3 doesn't work when MCLK & ULPCLK are different frequencies.

Russel Johnson

Part Number: MSPM0G3507

I have a requirement that the PD1 need to operate at high frequency (80Mhz) than PD0 and I want to get the UART3 (PD1 instance) working with DMA for receive & transmit. With my testing, I experience that as long as I keep both PD1 & PD0 clock the same (MCLK & ULPCLK), everything works fine, i see the data coming out on the pins. But if I have them at different frequency, DMA stops exchange, no data on the pin and no DMA interrupts triggered. But, if i write to TX FIFO directly from processor, UART is able to send them to the pins. I tried to read through the documentation but was not successful in finding a reason for this behavior.

From the block diagram of the device, i must be able to do this as CPU, RAM, DMA & UART-3 are in PD1 and they operate on same clock frequency.

Any help will be highly appreciated.

Russel

over 2 years ago

0 Luke Ledbetter over 2 years ago

TI__Mastermind 25620 points

Hi Russel,

I am looking into this and will get back to you tomorrow with more information.

Regards,

Luke

0 Russel Johnson over 2 years ago in reply to Luke Ledbetter

Prodigy 25 points

Hi Luke,

Do you have an update on this?

Regards

Russel

0 Luke Ledbetter over 2 years ago in reply to Russel Johnson

TI__Mastermind 25620 points

Hi Russel,

I was able to recreate what you are seeing by using the basic example uart_tx_multibyte_fifo_dma_interrupts.c . There are pre-production silicon uart and dma interactions that are getting fixed with the production silicon. I am contacting our design team to verify with them and will get back when I get information from them.

Without the DMA the UART peripheral still works at the 80MHz MCLK and 40MHz ULPCLK. (You also confirmed this by writing directly to the FIFO).
The DMA itself works at the 80MHz MCLK and 40MHz ULPCLK, you can verify this with the dma_fill_data example.
The DMA works with other peripherals (tested the DMA with the ADC using the adc12_max_freq_dma example)

Regards,

Luke

0 Russel Johnson over 2 years ago in reply to Luke Ledbetter

Prodigy 25 points

Hi Luke,

Thanks a lot for the reply. I will continue with my evaluation on other features that we are interested.

Regards

Russel

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MSPM0G3507: DMA writes to UART3 doesn't work when MCLK & ULPCLK are different frequencies.