Calculated CRC from FCE on the DMA data being transferred does not match with CRC in DMA register

[Kumaresh]

Hi,

I was trying to calculate DMA CRC but the calculated CRC from FCE does not match with CRC in DMA register.  Could pls look into the below query once you have time.

Question 1: How is the DMA checksum calculated in DMA_RDCRCR? I understand that CRC is being calculated for every DMA move but I am not clear on how these CRCs are being consolidated and represented in the RDCRC register. Could you please let me know if possible, on how the CRC calculated for DMA data transfer in Figure 1  ( Note : _dma​_1 is being transferred 1^st )

I am using this webpage http://www.sunshine2k.de/coding/javascript/crc/crc_js.html

Sunshine's Homepage - Online CRC Calculator Javascript

History. 2019/02/12: Added the support for 64bit CRC calculation and for binary string input. 2016/11/11: Added the option to print the CRC lookup table 'reversed'.

www.sunshine2k.de

 for CRC calculation

Some info on our DMA configuration is 

1. BLKM = 4
2. Transaction length = 0 i.e One transfer ( compressing 4 moves ) is One transaction
3. No byte swapping and
4. crc initial value is zero

Figure 1 : Debugger capture of DMA data transfer and checksum captured at end of DMA transfer

Figure 2 : Sample DMA move for the same dma channel with same configuration as above ( data is different from ones I used for calc in Fig 1 )

FCE configuration

Figure 3 : FCE settings for IEEE 802.3 CRC32

When I used to compute the CRC from the above webpage unless I gave the input data in 32 bits format with padding, I am not able to get the correct CRC as in above figure 1 for the same DMA data in 16 bits without padding. Does it mean that I can only give 32-bit data for 32 bit CRC calculation.

Input data with additional padding	Input data with no padding
CRC matches the calculated CRC from FCE as in Figure 1	CRC does not match with the calculated CRC from FCE

[Nambi]

Hi,

1. Could you let us know the device being used?(eg: TC2xx, TC3xx)

2. You can refer to the following thread. https://community.infineon.com/t5/AURIX/How-is-the-CRC-calculated-with-the-DMA/td-p/316676

3. You can refer to the Aurix Development Studio example FCE_CRC_1_KIT_TC397_TFT

Best Regards.

[Kumaresh]

Hi Nambi,

Thanks for sharing thread link but this one I already seen the data transfer is 32 Bit and for 32 Bit I can understand it. My question is for 16 bit ( data width ) how the checksum in dma computed.

We use TC37X.

[Kumaresh]

Hi, I understood on how DMA CRC is being computed. May I know how to calculate 32 bit CRC for 16bit data width using FCE.

[Nambi · Accepted solution]

Hi,

In FCE, the bit width of each word should be in terms of KERNEL polynomial width.

You would need to pad the 16-bit data.

Best Regards.