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Junior Member level 2
May 2, 2007
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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


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.

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

I need something between 10 and 50 Mbit/sec.

Good you also mention intended speed.

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

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

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.

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