DMA configuration for endianess swap for CRC

Stefan Steinmann

Other Parts Discussed in Thread: TMS570LS3137

Hi,

I'm using a TMS570LS3137. As I have to calculate a CRC over huge data ranges, I'm using the HW CRC module in Semi CPU Mode in combination with DMA transfer:

read size: 64bit

write size: 64bit

As the CRC registers are order in little endian, I would need to swap the high and low word directly during DMA transfer.

Is this possible with the DMA? Could I read 32bit and swap them before writing an entire 64bit value?

thanks, br

Stefan

over 11 years ago

0 Henry Nguyen over 11 years ago

TI__Expert 4225 points

Hi Stefan,

if you use tms570 device, then, if i remember correctly, the BE32 swap already done for you at DMA interface by hardware without user doing any extra configuration. Your crc result should be in big endian. can you please double check with just one data write To crc.

0 Stefan Steinmann over 11 years ago in reply to Henry Nguyen

Intellectual 410 points

No, the DMA based CRC is wrong in respect to Full CPU mode.

As in the memory map the PSA_SIGREGL comes before PSA_SIGREGH, the DMA just writes the lower word to PSA_SIGREGH and the higher word to PSA_SIGREGL.

In Full CPU mode a 64bit value needs to be swapped before writing it to the PSA_SIGREG, to ensure low word is going to low register and high word is going to high register.

Is there any possibility to perform such a transfer with DMA?

0 Henry Nguyen over 11 years ago in reply to Stefan Steinmann

TI__Expert 4225 points

stefan,

can you post your sample codes? if you don't want to post on public, please connect to me in private on this forum and you can send it to me. That would help us looking at the issue faster.

0 Stefan Steinmann over 11 years ago in reply to Henry Nguyen

Intellectual 410 points

Hi Henry, unfortunately I can't post my code.

But there are other CRC post already dealing with the fact that the high and low register of the CRC are swapped:

http://e2e.ti.com/support/microcontrollers/hercules/f/312/p/321430/1120745.aspx#1120745

http://e2e.ti.com/support/microcontrollers/hercules/f/312/t/104764.aspx?pi239031349=2

My question was just if it is possible to swap with the DMA the high and low word and write it as entire swapped 64 bit value?

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DMA configuration for endianess swap for CRC