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-   -   802.3 mii (http://www.fpgacentral.com/group/showthread.php?t=51226)

Paul 01-18-2004 08:39 PM

802.3 mii
 
Hi

can someone concisely explain what is 802.3 mii.
it seems my PHY chip has this function.
what does it do?
(i spend half an hour googling and still can't figure out what it does)
is it some higher level of abstraction that's easiler to interface?

why they design this chip with rx and tx in nibbles ?
why not bytes...

lxt972

Thanks

Marc Randolph 01-18-2004 09:36 PM

Re: 802.3 mii
 
Paul wrote:
> Hi
>
> can someone concisely explain what is 802.3 mii.
> it seems my PHY chip has this function.
> what does it do?


This sounds a little too close to homework for comfort.

Quoting from the LXT972 datasheet:

"provides a Media Independent Interface (MII) for easy attachment to
10/100 Media Access Controllers (MACs)."

Or said another way, it is supposed to make connecting to a MAC device
easy...

> (i spend half an hour googling and still can't figure out what it does)
> is it some higher level of abstraction that's easiler to interface?


Higher levels of abstraction almost always make things easier -
otherwise people wouldn't bother with the abstraction! The question is
how does it make things easier?

> why they design this chip with rx and tx in nibbles ?
> why not bytes...


Cause that is how MII is defined. Can you think of any reasons that, if
you were designing this interface, you might choose nibbles over bytes?
It sometimes helps to imagine specific examples in cases like this, so
here is one: imagine designing a 24 port Ethernet switch.

Have fun,

Marc



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