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Altera_Forum's avatar
Altera_Forum
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14 years ago

How can I get the signal from differential I/O pins

Hi, I need help.

I use differential I/O pins input. " dcoin_p", "fcoin_p", "data_ai_in_p", "data_aq_in_p" are the positive pins, and I define then in my program. But the negetive pins are not defined. There are warnings:

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Warning: Following 4 pins are differential I/O pins but do not have their complement pins. Hence, the Fitter automatically created the complement pins.

Warning: Pin "dcoin_p" is a differential I/O pin but does not have its complement pin. Hence, fitter automatically created the complement pin "dcoin_p(n)"

Warning: Pin "fcoin_p" is a differential I/O pin but does not have its complement pin. Hence, fitter automatically created the complement pin "fcoin_p(n)"

Warning: Pin "data_ai_in_p" is a differential I/O pin but does not have its complement pin. Hence, fitter automatically created the complement pin "data_ai_in_p(n)"

Warning: Pin "data_aq_in_p" is a differential I/O pin but does not have its complement pin. Hence, fitter automatically created the complement pin "data_aq_in_p(n)"

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I need the signal "dcoin", which is equal to the difference of dcoin_p and dcoin_p(n). In other words, dcoin=dcoin_p - dcoin_p(n), how can I get "dcoin" in my program? PS, I donot know how to use the dcoin_p(n) pin in my program and it seems can not be defined as a input .

Thanks a lot for every help.

2 Replies

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

    As Socrates says, set the pin as an LVDS input, but I assume you've already done this as the fitter is automatically creating the negative version. You don't need to get the dcoin as (dcoin_p - dcoin_n) - that's basically done for you by the I/O circuitry, so dcoin_p is the signal you want. I don't know what the I/O circuitry does if dcoin_p = dcoin_n.