Can Nios Read 128-bit-wide data?

Thanks for your reply.

Nowadays I know using Nios to read directly is efficient rather than DMA.

I will try more.

What exactly is your requirement?

If your requirement is that you must read a 128-bit data word in one clock cycle then you are going to have to either use a DMA controller or write your own little hardware component to do it.

If you're just trying to be efficient, using a DMA controller may not be the best solution if at the end of the day you've got to read the data using the NIOS anyway. Typically DMA is used when you need to transfer a large amount of data in as short amount of time as possible.

Jake

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No. NIOS has a 32-bit wide data bus. If you perform a 128-bit read, the NIOS will actually perform 4 reads to get the data.

Jake

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So , what if I use a DMA component to read 128-bit-wide data?

For example :

//////// Code start////////////# define TRANSFER_SIZE 2

int return_code ;

alt_dma_rxchan tx, rx ;

if( (tx= alt_dma_txchan_open("/dev/dma")) == 0 )

{

printf( "create dma failed" ) ;

return -1 ;

} if( (rx= alt_dma_rxchan_open("/dev/dma")) == 0 )

{

printf(" create dma failed" ) ;

return -1 ;

}

//// configure the DMA

alt_dma_txchan_ioctl( tx , ALT_DMA_SET_MODE_128 , (void*) (RAM_BASE) ) ;

alt_dma_rxchan_ioctl( rx , ALT_DMA_SET_MODE_128 , (void*)(DEST_BASE) ) ;

///// start transfer

return_code = alt_dma_txchan_send( tx , RAM_BASE , TRANSFER_SIZE , 0 , 0 ) ;

return_code = alt_dma_rxchan_prepare( rx , DEST_BASE , TRANSFER_SIZE , 0 , 0 ) ;

//////// Code end

Could I make it work?

No. NIOS has a 32-bit wide data bus. If you perform a 128-bit read, the NIOS will actually perform 4 reads to get the data.

Jake