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MSP430FR5728: Which of the MSP430FR series allow DMA transfer without active mode?

zguo
Intellectual 440 points
Part Number: MSP430FR5728
From the datasheet of MSP430FR572x, page 51, "6.10.8 DMA Controller": "The DMA controller reduces system power consumption by allowing the CPU to remain in sleep mode, without having to awaken to move data to or from a peripheral." Does it mean it can do DMA transfer in low power modes? As far as I know the FR59xx / 58xx / 59xx / 68xx / 60xx only allow DMA transfer in active mode. Are thee any other 430FR series which allow DMA transfer without active mode?
  • 0
    TI__Mastermind 20025 points

    Hi zguo, as my understanding, DMA of FR59xx / 58xx / 59xx / 68xx / 60xx is allowed in AM and LPM0 mode. CPU can be off during DMA transfer to reduce the power consumption. Could you please share the document or reason that "the FR59xx / 58xx / 59xx / 68xx / 60xx only allow DMA transfer in active mode". Thanks!

  • 0 in reply to Xiaodong LI
    Intellectual 440 points
    Thanks for the answer. I didn't know they allow DMA transfer in LPM0... My guess came from the datasheets. For example the datasheet of "MSP430FR596x, MSP430FR594x", on bottom of page 56, foot note (4): "(4) The DMA always transfers data in active mode but can wait for a trigger in any low power mode. A DMA trigger during a low power mode will cause a temporary transition into active mode for the time of the transfer." For the other FR59xx/... series the datasheets contain the same foot note. Back to the original question, in which LPM can DMA transfer data for FR57xx series?
  • 0 in reply to zguo
    TI__Mastermind 20025 points

    Thanks for your clarify. there are some unclear points on the power mode of DMA transfer as your mentioned. Please give me some time to check and confirm.

  • 0 in reply to zguo
    Guru 88700 points

    User Guide (SLAU272D) Sec 7.2.7 says that if MCLK is off it will be turned on (using the DCO) long enough to run the DMA cycle(s) then turned off again. The CPU will not execute any instructions.

    In the same sense: If main() is waiting in LPM, an ISR runs in Active (CPUOFF=0) mode, but we still refer (loosely) to the program staying in LPM.

  • 0 in reply to Bruce McKenney47378
    Intellectual 440 points
    So in the end it's power consumption is still much lower than moving data with CPU instructions, right?
  • 0 in reply to zguo
    Guru 88700 points

    Yes, on a per-word basis. Moving data is what the DMA does (it's pretty single-minded). And compared to waking up the CPU to move the data, it really wins.

    Don't forget to amortize the cost of loading all those control registers, though.

  • 0 in reply to Bruce McKenney47378
    TI__Mastermind 20025 points

    Hi zguo and Bruce, Thanks for your discussion and comment! the below items are confirmed: MCLK is used during DMA. CPU will sleep during DMA data transfer. I will close this thread now. and we will update a little bit on the description of MSP DMA document later

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