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TMS320F28386D: USB Boot OSC Frequency Limit

Frederick LIN
Intellectual 560 points
Part Number: TMS320F28386D
Other Parts Discussed in Thread: C2000WARE

Hi,

I am trying to use USB boot in F28386D with XTAL OSC 25MHz.

It showed unkown device in windows device manager.

I found some forms below said USB boot must use XTAL OSC 20MHz. And it success boot from USB after we changed it to 20MHz.

https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/858851/ccs-tms320f28388d-question-about-tms320f28388d-usb-boot-loader
https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/1044904/tms320f28388d-usb-bootloader-oscillator-frequency---does-it-have-to-be-20-mhz

Some question:

1. Does F28386D has the same limit about 20MHz to use USB boot mode?

2. I cannot find the description about the limit in F2838x TRM, where can I find the limit description in TI official documents?

  • 0
    TI__Mastermind 38275 points

    Hi Frederick,

    Frederick LIN said:
    1. Does F28386D has the same limit about 20MHz to use USB boot mode?

    Yes, this is true for all F2838x devices.

    Frederick LIN said:
    2. I cannot find the description about the limit in F2838x TRM, where can I find the limit description in TI official documents?

    I admit that the device clocking requirements for USB boot mode are not as clear as they should be. It looks like the device datasheet was meant to have the information, but it's still missing. I have reported this issue to be fixed in the next datasheet revision, sorry about that.

    In the last row of the table below from the TRM you'll see the required internal device clock frequencies. Basically the multiplier and divider values to reach those frequencies were chosen based on a 20 MHz external clock source.

    For further details you can look at the Boot loader source code ('bootloader_usb') files within the C2000WARE directory below:

    C:\ti\c2000\C2000Ware_4_00_00_00\libraries\boot_rom\f2838x\revA\rom_sources\cpu1\F2838x_ROM\bootROM\source

    Best,

    Kevin