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lan8710a power down mode

pavan krishna
Expert 1010 points

Dear All,

Could any one please help me to resolve in this issue,

I am using Beagle bone black with the OS running of "ti-linux kernel-3.12", there is a requirement that where I need to put my LAN PHY ( LAN8710A) of Beagle bone black in to power down mode during runtime. Can any one please advice me how can I put into the power down mode either from driver or user space application.

One more issue which I found was, once my board is completely boot-up, if I cut power to LAN PHY IC,  on the console I am seeing "U-Boot SPL******************" message periodically, I don't know what's happening, How can I solve this issue. Please help me to resolve this issue.

I hope that If we resolved the first mentioned problem, second will be eliminated.

Thanks in advance,

  • 0
    TI__Guru**** 393215 points

    Hi,

    Where is your LAN8710A reset signal connected? If it's connected to the processor warm reset please check if it doesn't pull this line low when power to the PHY is stopped.

  • 0 in reply to Biser Gatchev-XID
    Expert 1010 points

    Yes you are correct, the "sysreset" pin of LAN8710A making processor to enter into reboot mode when we cut the power to LAN. To resolve this issue, we isolated "sysreset" pin from processor(by providing switch) when we cut the power to LAN PHY IC.

    Thanks a lot,

  • 0 in reply to pavan krishna
    TI__Guru 61035 points

    You should check the LAN9710A data sheet to see the signals connected to AM335x are fail-safe. Most CMOS devices are not fail-safe, which means they do not allow any potential to be applied to pins when the device is powered off. If it does not have fail-safe IOs, you may not be able to power off the LAN9710A while other parts of the system have power applied. For example, the warm reset signal is pulled-up and some of the AM335X outputs connected to the LAN9710A may be high which would source a potential to the LAN9710A while it is powered off. This may violated the LAN9710A specification.

    This is not allowed on the AM335x device. For example, see the data sheet parameter “Steady State Max. Voltage at all IO pins” which states the IOs must never be greater than the respective IO supply + 0.3 volts. So if AM335x is powered off the maximum potential allowed on the IOs is 0.3 volts.

    Regards,
    Paul