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MCF52259 + 8041NL PHY fails at 100Mb

Question asked by paul humphreys on Jun 1, 2011
Latest reply on Jun 4, 2011 by paul humphreys



We are using MQX3.7 and Codewarrior along with the MCF52259 and the Micrel 8041NL PHY


The schematics from the tower board have be checked against our schematics and they are identical.


The only difference is that we have a POE power supply on our board.


Our board works 100% on 10Mbit over 100Metres of CAT5E cable but fails to work when the PHY is set to 100Mbit with any length of cable over 15 Metres.


The board is very tight for space and the POE components are very close to the Magnetics.


The noise on the 3.3V rail with the POE supply  is <50mV


The board functions 100% at 100Mb over 100 metres when the board is powered locally . ie 3.3V is applied and the POE is disabled


Has anyone had experience using POE with this Processor and Phy.


Thanks in advance