DP83848J: Power up Reset X1 clock requirements.

Part Number:DP83848J

Hi,

A question on the DP83848J chip.

Q: Is it required that the X1 25 MHz clock is started/applied within a specific time period after the PHY chip is powered up?

In our case the X1 clock is applied after approx. 3 seconds after that the PHY chip is powered up.
After that the X1 clock is applied on to the PHY chip we implement a delay of 256 ms before starting/applying the MDC (preamble) to the PHY chip.

This works without any problem most of the time the system is powered on.
But , at about a frequency of one of ca 100 system (PHY chip) power up's the MII interface of the PHY chip is not working, at the next power of the PHY chip the MII interface is working, and so on.
When the X1 clock is applied at the same time the chip powered on  this problem does not occur.

Thanks
Jan