topic Re: DMA CITER register modification on-fly in Kinetis Microcontrollers

DMA CITER register modification on-fly

davidzhou — Mon, 28 Mar 2016 21:04:22 GMT

Hi,

I have K60 and have written a DMA channel with dummy source / destination addresses. I need to modify the

DMA_TCD0_CITER_ELINKNO = DMA_CITER_ELINKNO_CITER_MASK;

CITER register value (reset to 0x7FFF), after certain numbfer of major loops. My question:

Is it thread-safe to modify the CITER register in another timer interrupt ISR?

Or have to stop the DMA operation and modify the register?

Thank you

David Zhou

Re: DMA CITER register modification on-fly

jeremyzhou — Tue, 29 Mar 2016 07:41:09 GMT

Hi David,

Please following the steps to modify the TCD register.

-disable the dma channel by clearing DMA Request Enable bit

-wait for DMA_TCDn.active = 0

-change the TCD to the initial configuration (to start from beginning)

-enable the dma channel by setting DMA Request Enable bit

Now once the dma channel is started again, it again loads TCDn to eDMA registers

and executes the minor loop according to the values in TCDn.

Hope it helps.
Have a great day,
Ping

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Re: DMA CITER register modification on-fly

davidzhou — Tue, 29 Mar 2016 12:23:46 GMT

Jeremy,

Thank you for your answer.

David