flexbus and DMA

AlexGiov — Wed, 25 Jan 2012 07:06:50 GMT

I've a question about flexbus on kinetis (I use K60).

I need to trasfer a large file from on-chip ram to an external memory connected on the flexbus. I need to do this with low CPU intervention.

is it possible wiht flexbus?

In other word can I copy a on-chip memory zone (from address A to addressB) out through flexbus?

In other word, again, Is it possible to use flexbus with DMA on Kinets?

thanks a lot for help.

AlexGiov

Re: flexbus and DMA

mjbcswitzerland — Wed, 25 Jan 2012 21:39:15 GMT

Yes, it is possible to perform a DMA transfer from internal memory to FlexBus memory.

Regards

Mark

Re: flexbus and DMA

ee — Fri, 11 May 2012 07:25:11 GMT

Here's a snippet from my K70 flexbus DMA code using CW10.2. I previously setup my flexbus for 32-bit transfers starting at address 0x60000000.

#define FLEXBUS_START_ADDRESS   0x60000000
#define NWORDS       1000
uint32   dmaBuf[NWORDS];

    SIM_SCGC7 |= SIM_SCGC7_DMA_MASK;
   DMA_CSR_REG(DMA_BASE_PTR,1) = 0;

       // major loop count (current = beginning)
   DMA_CITER_ELINKNO_REG(DMA_BASE_PTR,1) =
   DMA_BITER_ELINKNO_REG(DMA_BASE_PTR,1) = 1;
       // minor loop count (in bytes), word sizes
   DMA_NBYTES_MLNO_REG(DMA_BASE_PTR,1) = NWORDS << 2;
   DMA_ATTR_REG(DMA_BASE_PTR,1) =
              DMA_ATTR_SMOD(0)| DMA_ATTR_SSIZE(2)
           | DMA_ATTR_DMOD(0)| DMA_ATTR_DSIZE(2) ;

       // source addr, inc, end adj
   DMA_SADDR_REG(DMA_BASE_PTR,1) = (uint32)&dmaBuf;
   DMA_SOFF_REG(DMA_BASE_PTR,1) = sizeof(uint32);
   DMA_SLAST_REG(DMA_BASE_PTR,1) = -(NWORDS << 2);
       // dest addr, inc, end adj
   DMA_DADDR_REG(DMA_BASE_PTR,1) = FLEXBUS_START_ADDRESS;
   DMA_DOFF_REG(DMA_BASE_PTR,1) = 0;
   DMA_DLAST_SGA_REG(DMA_BASE_PTR,1) = 0;

DMA is now ready to loop through my dmaBuf, transfering all 1000 32-bit words out to a single flexbus location. I call this statement every 1ms (in my main systick event loop) to trigger it:

DMA_CSR_REG(DMA_BASE_PTR,1) |= DMA_CSR_START_MASK;

In the future I will add completion interrupts and error checking and such, but for now this minimal code seems to be doing the job quite reliably. DMA is a beautiful thing.

Steve Kaiser

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flexbus and DMA

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Re: flexbus and DMA