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Altera_Forum
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12 years ago

CYCLON IV GX - ALTGX Won't recieve any valid data

Hello I'm new in the forum, seems like very nice one me and my partner working on a final project for the university engineering degree. We have designed and manufactured two printed circu...
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Altera_Forum
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12 years ago

Ok, thanks, that is clearer.

So you have LVDS DC-coupled into a transceiver receiver channel on a EP4CGX50F484.

The common-mode voltage of LVDS is 1.25V, whereas the common-mode voltage of the receivers is 0.82V. In general I would have recommended AC-coupling these signals. However, "Table 1–2. Electrical Features Supported by the Receiver Input Buffer" in the Cyclone handbook indicates that DC coupling should be ok.

If you probe the signals at those receiver pins, how do they look, and what is the common-mode voltage?

Since you have an external termination, did you disable the on-chip termination (OCT)?

Cheers,

Dave