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Altera_Forum's avatar
Altera_Forum
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16 years ago

vhdl help

Hi,

In vhdl can we make an pin declared as "inout" to act as input or as output depending on certain condition.

entity rout is

port(

a : inout bit;

b : inout bit;

);

end rout;

i want "b" to act as output when a is input, and "a" as output when "b" is input.

I am using altera quartus 2 9.0 and i am getting this warning.

"Warning: The following nodes have both tri-state and non-tri-state drivers

Warning: Inserted always-enabled tri-state buffer between "a" and its non-tri-state driver.

Warning: Inserted always-enabled tri-state buffer between "b" and its non-tri-state driver."

what can i do to overcome this warning.

It may sound silly but i am a beginner and i need some help in this regard.

17 Replies

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  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Here is another confusing warning: Warning (15610): No output dependent on input pin "RXD".I have already used it like this "receiver PORT MAP (RXD,...,...); and "RSR<=RXD & RSR(7 DOWNTO 1)".How does this warning come from?

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    It probably means that any logic you have got in there has been synthesised away. Often this can come from unconnected clocks or enables stuck at '0'

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Nice reply!Thanks!

    Actually ,there are warnings about some output pins are stuck at GND this happened maybe when I didnot give their inial values.You know I can't give each value for each of them.so how to prevent them from being stuck at GND or synthesized away?
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Without seeing your code, I cant tell you what the problem is.

    My previous 2 reasons are just the most common causes of the "output not dependent on inputs" problem.
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    So do you know some common methods to solve it,like modify quartus settings ,the procedure or both?

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    normally, its a problem with your code rather than anything to do with quartus