TMS320F28388D: USB bootloader oscillator frequency - Does it have to be 20 Mhz?

Swapnil Patel

Intellectual 635 points

Part Number: TMS320F28388D
Other Parts Discussed in Thread: C2000WARE

Hi,

I have been looking around forum trying to find out more information about USB bootloader for TMS320F2838xD processors.

I came across post that indicated, USB bootloader requires 20 MHz Oscillator.

I might have missed the information explaining why that is, but can anyone help me understand why?

Is this hardware limitation, or included software limit?

Thaks,

Swapnil

over 2 years ago

0 Whitney Dewey over 2 years ago

TI__Guru 50575 points

You'll see there's a note in the data sheet stating that to meet the USB protocol accuracy requirements, the device's on-chip oscillator (INTOSC) can't be used, so the USB boot loader configures the the AUXCLK source to be the external oscillator and then configures the the AUX PLL. The multiplier and divider settings were chosen based off of a 20 MHz oscillator.

If you want to check out the boot loader code, you can find it in [C2000Ware installation]\libraries\boot_rom\f2838x\[rev]\rom_sources\

Whitney

0 Swapnil Patel over 2 years ago in reply to Whitney Dewey

Intellectual 635 points

Hi Whitney,

Will boot rom be ever updated to work with 25 MHz with later releases?

Swapnil

+1 Whitney Dewey over 2 years ago in reply to Swapnil Patel

TI__Guru 50575 points

No, there aren't currently plans to update it.

Note that if you're using a controlCARD, there are instructions in the User's Guide to switch from the 25 Mhz to 20 Mhz which would allow you to use the USB boot loader on the controlCARD.

Whitney

0 Swapnil Patel over 2 years ago in reply to Whitney Dewey

Intellectual 635 points

Okay, thank you for answer!

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TMS320F28388D: USB bootloader oscillator frequency - Does it have to be 20 Mhz?