Board to board serial link

[sythe]

I am thinking of connecting 2 Altera FPGA's together which are some distance apart, a few meters, over a high speed serial link.
Given the fact I do not have any IP except the basic IO cells (lvds, ddr etc) what is the best way to go ?
A few more requirements ; data width is 32 bit ; no clock recovery possible since the webpack of quartus is very limited, which means it must be a source synchronous.

Is it wise to have line encoding ?

best regards

ST

 

[FvM]

A "few meters" suggests a simple and interference immune interface standard, if the software overhead for a transformer coupled interface is unwanted, RS422 would be my first choice, in case of doubt using a simple UART protocol.

I don't agree with your considerations about Webpack limitations. There are ways to implement e.g. clock recovery with basic Altera inbuilt functions like PLL dýnamic phase shift. But UART is still simpler.

 

[sythe]

Checking on RS422 learned me that maximum data rate is around 10Mbit/sec.

I need something between 10 and 50 Mbit/sec.

 

[FvM]

Good you also mention intended speed.

Review RS-422 interface chip specifications. 40 Mbps is supported by many devices.

 

[sythe]

Wouldn't lvds be sufficient ?
It is directly available on the FPGA and avoids having external RS-422 drivers.

 

[FvM]

LVDS is basically suited. Question is if you can guarantee correct common mode voltage over "a few meters" for a galvanically coupled link. Also overvoltage protection for the FPGA inputs should be implemented.