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Original question:

TM4C1294NCPDT: Data discharge in not-connected to phy situation

TM4C1294NCPDT: TM4C1294 Ethernet PHY RO registor

GR
Expert 2961 points
Part Number: TM4C1294NCPDT

Hi

Are the RO type registers  Read Only?

I wrote Register 92: Ethernet PHY BIST Control - MR22 (EPHYBISTCR) @bit6 to 1.

(I think this register is RO.)

But softwere can write the register 1.

(MR22_BISTCR is user defined int value)

This picture shows UART output.

0x100 : before write MR22 (EPHYBISTCR) @bit6.(shows reset value)

0x140 : after write MR22 (EPHYBISTCR) @bit6 to1.

thanks,

GR

  • +1
    TI__Guru**** 184486 points

    Hi,

      I think it is a documentation error. There is also another bit LOOPBM (bit 17) of EMACCFG register that can be enabled for loopback mode when in MII mode. 

  • 0 in reply to Charles Tsai
    Expert 2961 points

    Hi Tsai-san.

    Thank you to your information.

    I understood that EPHYBISTCR bit6(TXMIILB) is RW Registor.

    Additional, I want to check.

    To set MII Loopback, Need to this?

    1. MAC Configuration : EMACCCFG BIT17(LOOPBM) sets 1.

    2. PHY Configuration : EPHYBISTCR BIT6(TXMIILB) sets 1.

    3.PHY Configuration : EPHYBMCR BIT14(MIILOOPBK) sets 1.

    thanks,

    GR

  • 0 in reply to GR
    TI__Guru**** 184486 points

    Hi GR-san,

      We don't have an example for MII interface to an external PHY and neither MII loopback testing. But if you get it to work using the above settings please let us know. I'm sure it will benefit others in the community. 

  • 0 in reply to Charles Tsai
    Expert 2961 points

    Hi Tsai-san

    I checked internal PHY using TM4C1294 EVM.

    For MII Loop back.Need to

    1. MAC Configuration : EMACCCFG BIT17(LOOPBM) sets 1.

    2.PHY Configuration : EPHYBMCR BIT14(MIILOOPBK) sets 1.

    I checked by see EPHYSTS(address 0x010, MR16) BIT3(MIILB) that is MII Loopback Status.

    I think EPHYBISTCR BIT6(TXMIILB)  used for BIST operation.

    thanks,

    GR

  • 0 in reply to GR
    TI__Guru**** 184486 points

    Hi GR-san,

      Thank you for your information.