Kinetis K64 MCU Ethernet Rx Errors in cold temperature

[JRIIS]

ABB need help on a field issue with there communication card using the NXP K64 MCU.

The issue is that when the ambient temperature is 10 degrees or below some adapters are not able to communicate over Ethernet after bootup.

ABB have reproduced this issue in weather cabinet and found out the reason is that the incoming packets from the MAC has the CR bit set (L is also set):

And thus ABB software discards the message.

What ABB have found out that only way to repair it after it’s in this state is to do a HW reset to the MCU. Software reset is not helping, the error bit stays on for all incoming messages.

And ABB have found also that the packets itself seems to be ok and are not corrupted, so if ABB just ignore the CR flag the communication is working ok. But then ABB can’t notice actually broken messages.

ABB found out also that if the MCU reset is kept down longer in power-up the issue is not appearing.

So the question is that for what reasons the CR bit is set by the MAC and what could affect it during the MCU reset?

In this card the MCU MAC is connected to a switch (Microchip ksz8863) with RMII. The switch itself is working normally when the issue appears.

Let me know if this can be addressed in this community or if I have to rapport it some ware else?

Thanks,

Jakob Riis

[JRIIS · Accepted solution]

We found an issue that was causing this issue:

In ABB HW there was a pin PTA5 from the MCU marked as the RMII_RXER input and it was also connected in software as that to the Ethernet MAC.But that pin was actually not coming from the phy, but was just connected to a test point and was left floating, apparently in cold boot this pin was left at value 1 which was seen also in the GPIO registers. ABB don’t fully understand yet why the value stayed at 1 after some cold bootups it didn’t go back to 0 after the module had warmed, but required the HW reset. But as a fix ABB have disconnected this pin from use in SW as it’s not anyway giving the error signal it was intended for.

/Jakob