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TMS320F28375S: Writing into F-RAM(8-bit accessible) from 16-bit DMA-SPI

Shreni P
Prodigy 110 points
Part Number: TMS320F28375S


Hi,

Iam trying to write data into F-RAM(FM25W256, 32K*8 Serial(SPI)F-RAM ) which is 8-bit accessible(TX/RX), from SPI configured in FIFO mode with the support of DMA in controller.

I need to transfer an array of 16-bit parameters each, when only 8-bit is accepted by FRAM, but transfer size(DATASIZE) is limited to a minimum of 16-bit value in DMA.

Please let me know, if there is any way to overcome this issue.

Thanks,

Shreni. P

  • +1
    TI__Guru* 81280 points

    Shreni,

    You are correct that the min transfer size of the DMA is 16-bit, this is true of the C28x core in general as it is a word based architecture.  In your case, you would just need to zero out the un-used 8 bits of the word and use the DMA to send that data to the SPI.  I beleive that the SPI data is left justified, so your data words would look like 0x??00.  The only penalty here is that each word has 8 bits of unused data, but there is no way around that if you are using the DMA.

    Best,

    Matthew