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CCS/MSP430F5659: USB Bootloader with 20MHz

Sandeep UD
Prodigy 110 points
Part Number: MSP430F5659

Tool/software: Code Composer Studio

Support Path: /Product/Development and troubleshooting/Common help topics when designing with TI devices/

Hi,

This thread is regarding MSP430F5659 controller, to implement USB bootloader. In the reference MSP430™ Programming With the Bootloader (BSL)( www.ti.com/.../slau319l.pdf), there is a hardware requirement as The USB Peripheral Interface requires the use of a high-frequency oscillator on XT2. For the BSL to function properly, the oscillator can be 24 MHz, 12 MHz, 8 MHz, or 4 MHz. But unfortunately in our circuit, its 20MHz. Like to know whether is there any work around to match the 20 MHz Crystal?

  • 0
    Guru 299840 points
    Section 42.2.3 of the User's Guide shows how to program the USB PLL; there is no combination of DIVM and DIVQ that would allow you to use a 20 MHz crystal.
  • 0 in reply to Clemens Ladisch
    Prodigy 110 points

    Thanks for your prompt response.

    So do you want to say that its not possible to implement USB bootloader with 20MHz???

  • 0 in reply to Sandeep UD
    Guru 299840 points

    See table 42-2 of a list of possible frequencies. For 20 MHz, the nearest values would be DIVQ=13,DIVM=31, which would result in a PLL frequency of 47.69 MHz. That would be an error of −6410 ppm, which is way above the 2500 ppm allowed by the USB specification, and has no chance of working in practice.

    USB cannot work with a 20 MHz crystal.

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