Making smart FIFO ?!

Hi,

Thanks for your answers brad and rysc.

1/ First idea : Make a fifo who strore data and his corresponding mask bits. Good idea but it may take up much place and it will be more complicated for me to read out easily my data... (check below to have more explanation of my issue)

2/ Second idea : Make an "aggregator" in order to wait to always have 256 bits to write in the FIFO. I think it's a very good idea but I don't know how to do this...

Well, I will give more information about my problem.

The function I need to realise is just like a texture mapping in image processing.

In my DDR2 memory, I have a very big size image (it's my texture image).

I need to extract a little image in this big image according to a position coordinate.

This coordinate can point to any bit in the big image and so, can point anywhere in the DDR address range. Obviously, it will point almost never to the first data bit of a DDR address...

From the DDR address who contains the first pointed bit, I can extract multiple blocks of 256 bits length. But first bits of the first data block will be useless (because they are before the correct pointed bit), and last bits of all last data blocks (at the end of each line of my little image) will be certainly useless too.

For every data block, I know which bits are included in the image to extract and which are not. But I don't know how to make an aggegrator to accumulate 256 correct bits before making a write operation in the fifo buffer.

Please, could you give me some tips to achieve my goal ??

How would you do that ?

Thank you very much in advance for your help.

See you.

Fabrice.