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20707 Discussions

Ethernet Link

Altera_Forum
Honored Contributor II
‎07-31-2008 05:24 AM
1,257 Views

Hi All, 

 

I have come across a very strange problem with ethernet board which has National's 83848M (Fast Ethernet) phy. When I connect this board with PC having Gigabit ethernet NIC or 10/100 Switch/Hub, 100 Mbps link established straight away. But when I connect same board with PC having fast ethernet NIC, link could not be established and nothing happens! I tried to get solution by giving reset to phy explicitly, but problem is not solved.  

Has anyone come across same problem? 

Your quick help would be highly appriciated! Thank you.
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Altera_Forum
Honored Contributor II
‎07-31-2008 06:05 AM
520 Views

Do the ethernet phys and transformers have an auto mdix system? If non of them have, you may need to use a crossover cable.

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Altera_Forum
Honored Contributor II
‎07-31-2008 06:35 AM
520 Views

Thanks Daixiwen! I know PHY has auto mdix, but I am not sure how to check whether transformer has it or not. And of course I know, I need to use crossover cable for point-to-point communication.

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Altera_Forum
Honored Contributor II
‎07-31-2008 06:45 AM
520 Views

An Ethernet transformer that is auto-midx compatible has the same circuits on the TX/RX pairs, to ensure that they can be switched by the PHY. But as you are already using a crossover cable, the problem doesn't come from mdix anyway. 

Do both ends have autonegotiation enabled? For the PC you can change this in the network driver settings usually, and for the PHY you must look for the correct MDIO registers. You could try disabling the autonegotiation and force both ends at 100Mbits/s.
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Altera_Forum
Honored Contributor II
‎08-05-2008 11:09 AM
520 Views

Yes, both end has auto-negotiation enabled. I tried by forcing at 100 Mbps but result is same. I have order new magnetic which is most compatible for 83848M phy, but if any one has come across this type of situation then please let me know how to solve it.

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Altera_Forum
Honored Contributor II
‎08-05-2008 12:32 PM
520 Views

I have come across some compatibility issues with certain Phys and auto-negotiation. 

 

It might be worth testing the setup with your fast (100M) ethernet PC but set both ends to the sme speed AND duplex. i.e. try with them both forced to 100M and Full Duplex. 

 

This could narrow the problem down to whether it is a signal integrity issue or an auto-negotiation compatibility issue 

 

Rgds 

 

Vern
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Altera_Forum
Honored Contributor II
‎08-05-2008 04:32 PM
520 Views

A signal quality problem can be checked by forcing one peer to 10 MBps/Half Duplex.

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Altera_Forum
Honored Contributor II
‎08-08-2008 09:32 AM
520 Views

Thanks everyone! Eventually I have solved the problem by replacing magnetic part. I had wrong magnetic on the board.

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