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AM1808 PinMux Utility discrepancy for RMII interface

TommyG
Genius 13045 points
Other Parts Discussed in Thread: AM1808

Used PinMux utility to generate registers setting for RMII interface on the AM1808 device.  The utility generated this setting for PINMUX15 register:

#define PINMUX15_VALUE 0x00000088

This sets PINMUX15_3_0 so that internal clock is driven on this pin for RMII interface.

According to DS, Table 5-102, Note 2:  Per the RMII industry specification, the RMII reference clock (RMII_MHZ_50_CLK) must have jitter tolerance of 50 ppm or less.

According to System Reference Guide, sec 6.3.4, Note: The SYSCLK7 output clock does not meet the RMII reference clock specification of 50MHz +/-50ppm.  SYSCLK7 is the internal clock which is output when PINMUX15_3_0 is set to 8 like the PinMux utility recommends.

My reading is that the pin mux utility is giving the incorrect setting for PINMUX15[3:0] nibble.  Can someone verify this and get the PinMux utility updated to give correct setting for PINMUX15 register?

Thanks.

  • 0
    TI__Guru* 84075 points

    Hi Tommy

    Acknowledge that for RMII , the clock is recommended to be sourced externally and not use SYSCLK7 and for that the PINMUX15_3_0 should be set to 0 (not 8).  This is also clarified in the EMAC clockign section of the Device Clocking chapter in the system guide.

    I will see what additional updates can be made to the PINMUX15 register description in the system guide to clarify this additionally.

    I will also talk with the pinmux utility owner to clarify this in the utility if possible and provide an updated version of the utility (might take a week or two to get this done).

    Let us know if you have any additional questions/concerns on this.

    Regards

    Mukul

  • 0 in reply to Mukul Bhatnagar
    TI__Genius 13045 points

    Mukul,

    Thanks for the response.  It will be good to clarify this as it is not consistently explained in our documentation.

    Could you post back here when updated utility is available?

    Thanks.

  • 0 in reply to TommyG
    TI__Guru* 84075 points

    Tommy

    The documentation updates are already in the pipe, we will likely have an updated version of the system guide by early June. This will put additional clarifications around the PINMUX15_3_0 definition.

    Same with the pinmux tool, I think we can have the fix available early June. I will update this post, once the updated utility is made available.

    Regards

    Mukul