ALT_INBUF_DIFF in cycloneII

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in my case it is a "modified" rs422.

can lvds pin work at 3.3 volt?

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"modified" RS422, that explains it all :-)

Quartus will give an error if you set Vccio to 3V3 and select LVDS as I/O standard.

I don't know what happens when you set Vccio to 2V5 in Quartus, but supply your bank with 3V3.

I guess there's a big chance LVDS will work, at least with your "modified" RS422.

But you don't get any guarantee from my side.

If you going to try it, please post the result.

Good luck, Ton