Help with debugging 10/100/1000Base-T PHY problem

Help with debugging 10/100/1000Base-T PHY problem

NewsGroups | Search | Tools
 comp.dcom.lans.ethernet  Post an article  get this group's latest topics as an RSS feed add this group's latest topics to your My MSN content add this group's latest topics to your My Yahoo content  add this group's latest topics to your Google content  YahooMyWeb Yahoo!  Google Google  Windows Live Favorites Windows Live  del.icio.us del.icio.us  digg digg  Add to Netscape Netscape
Subject Author Date
Help with debugging 10/100/1000Base-T PHY problem MM 07-31-2008
Posted by MM on July 31, 2008, 12:22 am
If you were  Registered and logged in, you could reply and use other advanced thread options
Hi all,

I have a design with a tri-speed Base-T PHY, which exhibits some weird
behaviour. For some reason sometimes the PHY doesn't establish the link with
another PHY (typically in a PC) after the auto-negotiation. Some of my
boards almost never fail, while others fail much more frequently.

I was wondering how people debug this kind of problems. Is there anything I
can look up with a basic 500 MHz scope? Is there a low level protocol tester
I could rent?


Thanks,
/Mikhail



home networking made easy, greater protection, less stress, introducing nm 5.0, 728x90
Posted by Marris on July 31, 2008, 12:43 pm
If you were  Registered and logged in, you could reply and use other advanced thread options
An obvious first step would be to read the PHY's status registers through
MDIO.

You need to check whether the capabilities you are advertising are
compatible with the PHY at the other side and whether the other side is
negotiating at all. You also need to check you are setting your PHY to
operate in accordance with the AN resolution function. Check that speed and
full/half-duplex have been set appropriately after AN completes.

Full/half-duplex needs the MAC to be configured properly.

Arthur.

> Hi all,
>
> I have a design with a tri-speed Base-T PHY, which exhibits some weird
> behaviour. For some reason sometimes the PHY doesn't establish the link
> with another PHY (typically in a PC) after the auto-negotiation. Some of
> my boards almost never fail, while others fail much more frequently.
>
> I was wondering how people debug this kind of problems. Is there anything
> I can look up with a basic 500 MHz scope? Is there a low level protocol
> tester I could rent?
>
>
> Thanks,
> /Mikhail
>



Posted by MM on July 31, 2008, 1:08 pm
If you were  Registered and logged in, you could reply and use other advanced thread options
Hi Arthur,

Thank you for your help. I have two scenarios. In one I read all ones from
all the MDIO registers, so in other words the chip seems to be in some bad
state, and nothing can be done to revive it through software. This condition
seems to depend on power-up and it could be a separate problem. In another
scenario I can read/write MDIO registers fine however the link is not
established. I know that the problem is on my side because a) the same card
might work/not work without changing anything on the other side, and b) I
can take another of my cards from the same batch and it will work...


/Mikhail




> An obvious first step would be to read the PHY's status registers through
> MDIO.
>
> You need to check whether the capabilities you are advertising are
> compatible with the PHY at the other side and whether the other side is
> negotiating at all. You also need to check you are setting your PHY to
> operate in accordance with the AN resolution function. Check that speed
> and full/half-duplex have been set appropriately after AN completes.
>
> Full/half-duplex needs the MAC to be configured properly.
>
> Arthur.
>
>> Hi all,
>>
>> I have a design with a tri-speed Base-T PHY, which exhibits some weird
>> behaviour. For some reason sometimes the PHY doesn't establish the link
>> with another PHY (typically in a PC) after the auto-negotiation. Some of
>> my boards almost never fail, while others fail much more frequently.
>>
>> I was wondering how people debug this kind of problems. Is there anything
>> I can look up with a basic 500 MHz scope? Is there a low level protocol
>> tester I could rent?
>>
>>
>> Thanks,
>> /Mikhail
>>
>
>



Posted by Marris on September 6, 2008, 1:33 pm
If you were  Registered and logged in, you could reply and use other advanced thread options


If you are reading all ones, MDIO is not connected at all. The serial MDIO
line is pulled high by default.

If you can read the status registers then you should have enough information
to discover why you have a problem. First compare your advertised ability
with your link partners ability. This will tell you if there is a compatible
mode of operation. If there is not then the link will not come up. If there
is check you are configuring to match it. For example if your link partner
is requesting 100Meg operation make sure you are not operating at 1G.

> Hi Arthur,
>
> Thank you for your help. I have two scenarios. In one I read all ones from
> all the MDIO registers, so in other words the chip seems to be in some bad
> state, and nothing can be done to revive it through software. This
> condition seems to depend on power-up and it could be a separate problem.
> In another scenario I can read/write MDIO registers fine however the link
> is not established. I know that the problem is on my side because a) the
> same card might work/not work without changing anything on the other side,
> and b) I can take another of my cards from the same batch and it will
> work...
>
>
>



Similar ThreadsPosted
Routing problem December 12, 2005, 3:48 pm
Problem with WAP and LAN connection September 4, 2006, 7:21 am
Problem: UTP only works at 10 MHz July 27, 2007, 8:02 pm
problem on LAN or firewall November 22, 2007, 7:21 am
baffling speed problem July 23, 2005, 2:52 am
Problem with Crossover Cable August 28, 2005, 1:18 pm
Problem with 2 NAT boxes behind a router February 10, 2006, 12:23 pm
Network configuration problem September 7, 2007, 7:23 am
100BASE-TX Scrambler Problem June 12, 2008, 9:04 pm
3Com switches and 1000Base SX problem July 14, 2005, 9:45 pm

other useful resources:
The Federal Communications Commission (FCC)
Telecommunications Industry Association
Electronic and Software Security Products and Services
International Telecommunication Union

Custom CGI Perl and PHP programming by 1-Script.com

Contact Us | Privacy Policy
The site map in XML format XML site map