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[OMAP-L137] USB_REFCLKIN

Andreas Weishaupt
Expert 1270 points
Other Parts Discussed in Thread: OMAP-L137

Hi,

I'm working with the C6747 of the OMAP-L137 EVM from Spectrum Digital. In my application I use McASP0 only in receive mode. Now I need to transfer data to a host by USB. I've seen that USB_REFCLKIN is pin-muxed with AHCLKX0, the McASP0 transmit master clock.

1) do I need to pin-mux USB_REFCLKIN in order to use the USB controller?

2) if the answer to 1) is yes: since I don't need McASP0 to transmit, would pin-muxing USB_REFCLKIN affect the proper working of McASP0?

And a last question: why can't I select USB in the pin setup utility?

Thank you very much.

Andreas

 

  • 0
    TI__Expert 8785 points

    Andreas,

    USB_REFCLKIN pin is used as a reference clock whenever AUXCLK cannot operate at one of the allowed input frequencies to the USB2.0 subsystem (12, 13, 19.2, 20, 24, 26, 38.4, 40, 48Mhz).   If AUXCLK is a valid frequency, USB_REFCLKIN is not needed, so AHCLKX0 can be selected.

    For more information on USB_REFCLKIN and the USB clock control, please see the Device Clocking section of the C6747 System Reference Guide.

    On the pinmux setup utility, USB is excluded because most of the pins do not require pinmuxing (ie, USB0_DM, USB0_DP, USB0_ID, etc).  If needed, you can manually select a pin by double-clicking on the cell.

    - Christina

  • 0
    TI__Expert 7435 points

    You can use USB without the need for USB_REFCLKIN external clock.  By default we use the internal reference clock.

    regards

    swami