M52259 TOWER - problem with reading PHY

[mjbcswitzerland]

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

[mjbcswitzerland]

Hi All

I believe that I could resolve the issues now.

1) In the backplane board (TWR-ELEV FUNCTIONAL) there was a short circuit between the bus lines A57 and B57 meaning that the 5V USB voltage was short circuited with the interrupt line and the FEC_MDC line. This is probably a board defect since it is not visible. A second such board was OK.

2) The PHY takes some time to react after a reset. This is different to the DEMO board but not a big problem - if I poll it for a while it will then start sending responses.

3) However 2 alone didn't fix it completely. Due to the backplane capacitance and a 4k7 pull-up on the FEC_MDO line the rise time when reading the signal is too slow to read it at 2.5MHz (standard speed). When the PHY starts responding values were being read as 0x0000 since the '1's were not rising to more than a volt or so. By slowing the clock to 700kHz (slowest possible with 80MHz PLL setting) it then reads correctly, although the signal is not really a square wave yet. A stronger pull up would be recommended in this case.

Regards

Mark

[mjbcswitzerland]

Hi All

Recently I received an TWR-LCD board to go with the basic Tower Kit.

After adding some graphical support I have added this video showing it in operation - note that it also shows a temperature/humidity sensing application based on a new SENSIRION sensor (SHT21 - via I2C).

http://www.youtube.com/watch?v=AdtRyQ-2IrE

Regards

Mark