Mark Butcher

M52259 TOWER - problem with reading PHY

Discussion created by Mark Butcher on May 19, 2010
Latest reply on Oct 3, 2010 by Mark Butcher

Hi All

 

Does anyone have experience with reading the Micrel PHY on the Tower board?

 

These are the difficulties that I had/am having.

 

1) Since the PHY was reading only 0xffff the management signals were verified. It turned out that the clock was missing but TX data was seen. This was only the case when the TWR-SER board is inserted and the signal is then pulled to a voltage of about 4.4V. When the backplane track to pin B57 (IRQ5) is cut this problem is resolved and the clock is seen as normal.

 

- on the TWR_SER board IRQ5 is connected to two optional jumpers but none are mounted so where this 4.4V signal origiates from is unclear.

 

2) After making the backplane change the Ethernet interface operates (unlike on the DEMO board the configuration of the PHY has to be actively driven under SW control and without that it seemed to power up in isolation mode and so does nothing) the PHY can still not be read. Various PHY addresses were driven during PHY reset and all possible PHY addresses are polled to see whether one responds, but no reaction.

 

- for comparison, on the DEMO board it was always possible to read the PHY on address 1.

 

3) A second TWR-SER board (from a V1 kit) was tested as well and the behaviour was identical (Ethernet OK, PHY can not be read, 4.4V on the IRQ5 line which short circuits the FEC_MDC [when backplane track not cut])

 

Does anyone else have experience?

As far as I known the standard SW delieverd with the kits doesn't check whether the PHY read operates - since Ethernet does still work, maybe such a problem has been overlooked (?)

 

Regards

 

Mark

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