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Altera_Forum's avatar
Altera_Forum
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12 years ago

LVDS TX as LVDS receiver in Cyclone V

Hello, In a new design I have to interface a few 8-channels ADCs to a Cyclone V GX C9F31.The ADCs use LVDS signaling at 240 MHz DDR.

In a previous design I've used Cyclone IV and any LVDS pair could be used for either output (true or emulated LVDS) or input.

Now for Cyclone V my understanding is that only the LVDS_RX can be used as receivers.

It this really the case?

Quartus II (13.1) fitter complains if I try to assign an input with LDVS io-standard to a LVDS_TX pair.

The Cyclone V handbook mention that the other way around is possible (use a RX pair as emulated TX) but no word for my case.

Many Thanks in advance

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    12 years ago

    Yes, this really is the case. You will not be able to drive a differential signal into a DIFFIO_TX_xxx channel. Differential input signals will have to go into DIFFIO_RX_xxx pins.

    Note: emulated LVDS does allow DIFFIO_RX_xxx pins to be driven.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    12 years ago

    Thanks for the information.

    I'll have to use more banks for the ADC readout.

    Nice to have deserializer in hardware thou.

    As a comment, It would be helpful to have a list of the new features/limitations with respect to the previous device in the family (e.g. EPC5 vs. EPC4) in the Handbook.