Posted on May 17, 2011 at 09:42Who ever came up with the idea of making ouputs (LEDs) as inputs (strapping pins) caused me a lot of grief, but perhaps the problem you are experiencing is as follows:
the PHY comes up as device 17, but it is set to auto link and begins flashing it's LEDs. Then you hit it with a reset and because the LEDs have some capacitance, they override the weak strapping resistors, so the moment the PHY comes back to life, it misreads your strapping pins.
This is exactly what happened to me. The strapping pins requested device 0x01, but a flashing LED caused it to move to 0x05 on fast reset. The solution was to change the reset time to be much longer, to allow the weak strapping resistors to actually drain away the residual charge from the pins.
One thing you can do is try to read say register #1 from all possible PHY addresses, and see if anything surprising comes up. This is how we discovered address 0x01 changed to 0x05.
I think in addition, address 0x00 comes up as a global address, but everything I've heard about it is to avoid using it.
