[SI-LIST] Re: Buffering 125MHz GMII signals
- From: "Henrik G. Madsen" <hgm@xxxxxxxxxxx>
- To: <samir.gundawar@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Wed, 16 Apr 2003 10:58:25 +0200
Hi Samir
Use a better MAC or ... ;-)
You can use a simple 74LVCH16374 or similar device to buffer the data, =
and a small zero delay clock buffer for the clock.
The output of the clock buffer should clock the xxx16374 and the =
receiver.
By using this approach you are changing the timing of the GMII data from =
a t(su) and t(h) compared to the rising edge of the clock to a t(pd) =
compared to the rising edge.
The skew between the individual outputs does not matter in the above =
approach.
The delay through the flip-flop should be short enough not to violate =
the required setup time at the receiver and long enough not to violate =
the hold time at the receiver.
Most newer xxx16374 has a specified min and max t(pd).
Regards
/Henrik G Madsen
-----Original Message-----
From: Samir Gundawar [mailto:samir.gundawar@xxxxxxxxx]
Sent: 15. april 2003 12:46
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Buffering 125MHz GMII signals
Hello All,
I am using one Intel GIGMAC on our board and trying to interface the
GMII signals from MAC to other GMII device on daughter card.
=20
When we simulated the GMII signal, we found that driver is not capable
of driving 10 inches of PCB Traces.
=20
In this situation, is it a good idea to buffer the GMII signals(along
with the clock)? Have anybody tried buffering the 125MHz GMII signals in
Past?
=20
If yes, can you pl suggest the buffers used at this high frequency?
=20
I think this buffer should also have Very low pin to pin skew (to meet
the timing margins) and very fast driving capability.
=20
Does anybody have any suggestions what other care should be taken in
choosing this buffer?
=20
Any kind of suggestions will be a great help...
=20
Thanks in Advance...
=20
Rgds,
Samir
=20
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