Re: LTX971 link error

From: George Varndell (gvarndell_at_hotmail.com)
Date: 04/03/04 

Date: 3 Apr 2004 03:19:05 -0800

> > >
> > > Has someone experience with the LXT971 from LevelOne(Intel).
> > > I've done designs with LXT970 and MPC8260. They always worked without
> > > problems. Now I'm using the LXT971 with MPC8270 the first time in a
> > > new design and have problems in establishing the link. After auto
> > > negotiation I have a link for some seconds.
> > > Then the link is broken and the auto negotiation starts again. I'm not
> > > sending any data over the Ethernet. The design is strict made with the
> > > application note from the data***. If I disable Aneg the problem is
> > > the same.
> > > I've measured all signals, power supply,clock and the differential
> > > analogue signals. Nothing obscure.
> >
> > Just a shot in the dark from a non-H/W engineer who recently
> > witnessed a similar problem. Are you using a crystal?
> > The 971 seems highly vulnerable to small clock jitter.
>
> Thank you,
> we are using a oszillator ship, and have therefore no significan jitter.

But, in our case, an oscillator was the problem. Our H/W guy installed
a crystal and the problem went away. Like you, he thought the osc was
good enough but it wasn't. With the osc, when forced into 10BaseT mode,
the 971 could communicate with its peer. Autoneg simply wouldn't work
and forcing 100BaseT caused nearly 100% CRC errors on received packets.

Regards,
George Varndell