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ALTGX: Byte Ordering is disabled when Rate Match FIFO is enabled

Honored Contributor II

I'm working on Cyclone IV ALTGX @ basic mode, x16, loopback and use Quartus 13.  

I want to enable Byte Ordering. The issue is that when Rate Match FIFO is enabled, Quartus automatically disable the Byte Ordering. 

I do need Byte Ordering since data are coming in reverse byte order.  


1. Why there is a relation between the two Byte Ordering and Rate Match FIFO ? 

2. Is this limitation only in Cyclone IV or Quartus 13 ? 

3. If I do want Rate Match FIFO is that mean I had to implement Byte Ordering on the Fabric ?  


Another Q regards to Rate Match FIFO and x16 mode, 

assuming stream is already byte ordered. Is there a guarantee that Rate Match FIFO will add/remove skip bytes in such it keep steam byte order (i.e., 2 bytes or 4 bytes) not to break the byte ordering ?  

Handbook mention only that Rate Match FIFO will remove SKP as long as there is at least one SKP in the stream; add up to 4 at most there is up to 5 SKP is the stream.  


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