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AM335x MII in Pinmux tool

Daniel Brown
Intellectual 870 points

Other Parts Discussed in Thread: TMDSICE3359, AM5728

Hello,


What is the difference between the MII and the MII_PRUSS1 shown in the pinmux utility (see attached picture)? Which of these peripherals is the one
used on the Beaglebone Black?

Thanks.
Dan

  • 0
    TI__Guru**** 393215 points
    Hi,

    MII is the CPSW external port, and MII_PRUSS1 is the Industrial Ethernet port inside the PRU peripheral. For general purpose Ethernet you should use the CPSW.
  • 0 in reply to Biser Gatchev-XID
    Intellectual 870 points
    Biser,

    Thanks. So I have these follow-up questions:

    1) The MII and MII_PRUSS1 do NOT seem to share the same pins. Is that true?
    2) Are they both compatible with traditional 10/100M MII Ethernet PHYs?
    3) The signal pr1_mii0/1_rxlink signal seems to only exist for the MII_PRUSS1. Why?
    4) I want to implement one of these ports as an EtherCAT master port. The other port
    I intend to use as a generic Ethernet port for management, debug and initial programming.
    From what I can tell I do not necessarily need to use the industrial port, the MII_PRUSS1, for the EtherCAT
    master implementation, correct?
    5) Would there be an advantage to using the MII_PRUSS1?

    Dan
  • 0 in reply to Daniel Brown
    TI__Guru**** 393215 points
    EtherCAT Master should be implemented on the CPSW. It doesn't require PRU usage, and we don't have examples for PRU implementation of this.
  • 0 in reply to Daniel Brown
    TI__Mastermind 44306 points
    Daniel,

    1) The MII and MII_PRUSS1 do NOT seem to share the same pins. Is that true?
    Yes, internally there are different signals and in some cases they do not overlap in pin-muxing to a pin. See the TMDSICE3359 schematics for an example.

    2) Are they both compatible with traditional 10/100M MII Ethernet PHYs?
    Yes. See the datasheet for details.

    3) The signal pr1_mii0/1_rxlink signal seems to only exist for the MII_PRUSS1. Why?
    It is an input to PRU-ICSS and can be used to quickly detect link loss. Usage is defined by software however.

    4) I want to implement one of these ports as an EtherCAT master port.
    If you look at latest RT-Linux SDKs you will find the PRU-ICSS ports supported as standard ethX devices. So you may run any EtherCAT master that has a standard driver here. I personally tested 3S/CoDeSys EtherCAT master (however on AM5728 PRUs...) but there are other vendors that can provide solutions. Even the free SOEM should work.

    5) Would there be an advantage to using the MII_PRUSS1?
    CPSW dual-EMAC mode works but the two ports are not totally independent. E.g. they share counters... If you use one port CPSW and one port PRU-ICSS there is no dependency at all. May be an advantage in some use cases.

    Regards,