Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
9 years ago

How to use LVDS pins on CycloneIV bank8 for receive?

I need to configure LVDS receive pins on bank8 of cycloneIV. It is dedicate to LVDS receive but not LVDS TX. I saw on handbook said on bank8 the LVDS do not support true LVDS for tx and need to addtinonal resistors externally. How about LVDS receive of bank8? Is a 120ohm resistor in between of diffio_p and diffio_n able to implement LVDS recevie on bank8?

Dose it mean on all banks of cycloneIV, the LVDS receive just need such a 120om resistor no matter true LVDS or not?

3 Replies

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

    Hi,

    Yes for RX you need only termination resitor and handbook states that it should be 100ohm.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    9 years ago

    Thanks for the quick reply.

    Another I am not quite sure : Are all the LVDS pairs bidirectional? For example, DIFFIO_T8p and DIFFIO_T8n pair is able to be configured as both LVDS rx and LVDS tx(emulate LVDS). Becasue of it is DIFF'IO'.

    Is my understanding correct?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    9 years ago

    That's correct - for Cyclone IV. Newer families - including Cyclone V - have dedicated Tx & Rx pairs. So, that wouldn't be the case.

    If in doubt, try it. Run it through Quartus with the pin assignments you want. Quartus will tell you if it's invalid.

    Cheers,

    Alex