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RE: 100 MB Ethernet problem



I would also add the following in case it helps anyone else with similar
Ethernet issues we had in getting a custom board going:

We also found issues with the 25 MHz ref clock. 
The circuitry from the the Axis dev board (well the Axis 82 
dev board we started with anyway) is probably not going to meet 
the specifications for the Broadcom chip. If you read the specs 
they specify a +/- 50 ppm clock with a 50% duty cycle (+/- 10%)
and edge rates from 1ns to 4ns(10% to 90%). 
If you use the clock circuitry of the development board I think 
you will find that you will have a difficult time meeting 
those specs especially as regards variation in parts, temperature, etc.
We switched to a master clock oscillator circuit - one of 
those all-in-one devices in a single package such as from CTS 
rather than the discrete oscillator circuitry that the dev board used. 
Once we did that and followed all the Broadcom Ethernet 
pc-board layout recommendations (VERY IMPORTANT!!!) all the 
mysterious Ethernet problems went away.

Regards,

Dave

> -----Original Message-----
> From: owner-dev-etrax@xxxxxxx.com 
> [mailto:owner-dev-etrax@xxxxxxx.com] On Behalf Of Zhuorong Deng
> Sent: Tuesday, June 29, 2004 9:45 AM
> To: Mikael Starvik
> Cc: dev-etrax@xxxxxxx.com
> Subject: 100 MB Ethernet problem 
> 
> 
> Hi, Mikael:
> 
> I found the problem, which is the 25MHz Ref clock to
> the PHY is unstable with the PLL filter components in
> the recommended value from the datasheet. I have to
> change the 680pf capacitor to be 0.022uf to make the
> clock being more stable. After this, the unit works
> fine with the 100MB network because I can see file can
> be transfered at the rate of about 33MB/sec with ftp.
> flash update image is also working with 100MB network
> now.
> 
> I also post this to dev-etrax@xxxxxxx.com and hope it
> will help someone with the similar problem.
> 
> Regards,
> 
> Eric
> --- Mikael Starvik <mikael.starvik@xxxxxxx.com> wrote:
> > In the output you can see that the Rx frame counter increases.
> > This indicates a receiver problem as you say. I
> > would say
> > that this is a hardware problem (such as bad routing
> > and/or
> > bad impedance). I am not really a hardware guy so I
> > can't
> > really give any pointers on where to start.
> > 
> > -----Original Message-----
> > From: Zhuorong Deng [mailto:zhuorongdeng@xxxxxxx.com]
> > Sent: Friday, June 25, 2004 5:32 AM
> > To: Mikael Starvik
> > Subject: RE: 100 MB Ethernet problem 
> > 
> > 
> > Hi, Mikael:
> > 
> > I attch the result of the ifconfig with this mail.
> > It
> > is from a unit/hub combination that works with ping
> > but fail with ftp. It does not show many packet
> > error
> > or packet fropping.
> > 
> > If I use another hub with the unit, the ping will
> > fail. Most of the time, I don't see the Rx packet
> > count increased when the unit is being pinged.
> > Sometimes I can see one or two packets coming in and
> > then I will get the Reply for one or two times. It
> > looks like the Rx end is having trouble. Any
> > suggestion?
> > 
> > Regards,
> > 
> > Eric
> > 
> >