MII Connection problem

alessandromaggi — Wed, 17 Jan 2018 12:48:43 GMT

Hi,

I have a custom board(designed by us) based on IMX6 SoloX. This board has (among other) two optical ports 100-FX, realized connecting a micrel KSZ8873FLLI via MII to the SoloX.

The problem is that I found an unexpected electrical level on the MII interface in TX direction. I would like the high level to be 3.3V, but on the oscilloscope I quite often can see a stable level around 2 volts.

So on the TX line I can see 3 different voltage level: 3.3V (expected igh level), 2V (unexpected and unwanted high level), and 0V (low level).

Of course with this condition the port is not working.

My question are:

1) Is it possibile for the SoloX to work with an MII interface with 3.3V as high level ? The reference manual is not very clear on this topic.

2) If yes, how the NVCC_SGMII should be connected ?

3) What can cause this strange 3 level signal ?

Re: MII Connection problem

igorpadykov — Wed, 17 Jan 2018 23:42:36 GMT

Hi Alessandro

one can recheck enet power supplies connections using

i.MX6SX Datasheet Table 110. 19x19 mm Functional Contact Assignments

"Power Group" column
https://www.nxp.com/docs/en/data-sheet/IMX6SXCEC.pdf

Also one can look for layout errors and short circuit between traces.

3.3V is allowable value according to Table 10. Operating Ranges i.MX6SX Datasheet.

Best regards
igor
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MII Connection problem

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