Correction to the "Ethernet problem"

Chris Johns chrisj at rtems.org
Wed Feb 6 05:09:53 UTC 2008


Leon Pollak wrote:
> 
>> Does you firmware initialise the PHY at all or do you expect it to come
>> up in the correct state?
> The PHY does auto-negotiation. The spec says that this may take 2-3s after 
> reset. I give it about 14-16s as minimum and it is still not enough!?
> 

What does the PHY say is happening ? It is the simplest way to rule the PHY in 
or out.

Experience with different PHY devices and switches has taught me to follow the 
IEEE standard for the MII type PHY devices and to monitor the status registers 
and act on the results. I am not saying this is your specific problem, rather 
I would not expect the device to act automatically for you in all cases.

You should also monitor the PHY during operation. What happens if someone 
pulls a cable, turns the switch off, or moves the cable to a port that is half 
duplex and you are configured for full duplex ?

Implementing monitoring and support is more work but the results out way the 
time involved.

Regards
Chris



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