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Clock and frame sync on LVDS link, Cyclone 5

Honored Contributor II

Hi all, 

I am to design a connection between two cyclone 5 gx on our upcoming boards. There shall be 4-16 bidirectional links with speed 300-800mb each, 

running on kind of backplane + boards assembly. 

I would like to avoid using transceivers due to its limited count and higher cost of FPGAs. 

Also, I would like to keep just minimal count of wires for each link (1 pair for Rx, one for Tx, no clocks, no frame sync) if possible. 


So I am considering to implement simple "transceiver like" approach using lvds but with slower frequencies.  


My raw idea: 

- Rx side with ALTLVDS_RX plus external PLL + 8/10 decoder in LEs 

- "some" logic to sync frames.. I could transmit special pattern or to use "start-stop" or other technique ? 

- Tx side with ALTLVDS_TX + 8/10 encoding and "some" training state logic 

- Mutual feedback about "locked" state 


Since I am to design both side of communication, I am free to implement whatever approach is feasible. 

On the other hand I am quite a newbie, so this will be a big challenge in all cases :cool: 


I would appreciate any opinions from you - experienced guys. 

Could you say if it is viable solution or to suggest other approach ?  

Also any related resources/examples are welcome. 



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