SLAA457B September   2013  – October 2018 MSP430F5500 , MSP430F5501 , MSP430F5502 , MSP430F5503 , MSP430F5504 , MSP430F5505 , MSP430F5506 , MSP430F5507 , MSP430F5508 , MSP430F5509 , MSP430F5510 , MSP430F5513 , MSP430F5514 , MSP430F5515 , MSP430F5517 , MSP430F5519 , MSP430F5521 , MSP430F5522 , MSP430F5524 , MSP430F5525 , MSP430F5526 , MSP430F5527 , MSP430F5528 , MSP430F5529 , MSP430F5630 , MSP430F5631 , MSP430F5632 , MSP430F5633 , MSP430F5634 , MSP430F5635 , MSP430F5636 , MSP430F5637 , MSP430F5638 , MSP430F5658 , MSP430F5659 , MSP430F6630 , MSP430F6631 , MSP430F6632 , MSP430F6633 , MSP430F6634 , MSP430F6635 , MSP430F6636 , MSP430F6637 , MSP430F6638 , MSP430F6658 , MSP430F6659 , MSP430FG6425 , MSP430FG6426 , MSP430FG6625 , MSP430FG6626

 

  1.   Starting a USB Design Using MSP430™ MCUs
    1.     Trademarks
    2. 1 USB and the Art of Making Something Complex Look Simple
      1. 1.1 What Has Made USB So Successful?
      2. 1.2 But It Looks So Simple!
      3. 1.3 TI's Approach for MSP430 USB
    3. 2 MSP430 USB Silicon
      1. 2.1 How MSP430 Devices are Documented
      2. 2.2 USB-Equipped MSP430 Derivatives
      3. 2.3 MSP430 USB Module
      4. 2.4 USB Certification of the Silicon
    4. 3 Software
      1. 3.1 USB Developers Package: Overview
      2. 3.2 USB API Stacks: Features
      3. 3.3 MSP430 USB Descriptor Tool
      4. 3.4 Host Software, and the Java HID Demo App
      5. 3.5 USB API Programmer's Guide and Examples Guide
      6. 3.6 MSP430 USB Field Firmware Upgrade Tools
    5. 4 MSP430 USB Hardware Design
      1. 4.1 TI Reference Design for USB Interface
      2. 4.2 Selecting a Power Configuration
      3. 4.3 Selecting a Clock Configuration
        1. 4.3.1 Choosing a Source
        2. 4.3.2 Choosing a Frequency
      4. 4.4 Other Reference Design Commentary
    6. 5 MSP430 USB Software Design
      1. 5.1 How to Choose a USB Device Class
      2. 5.2 How to Select a Vendor ID (VID) and Product ID (PID)
        1. 5.2.1 What are the VID and PID?
        2. 5.2.2 How are They Chosen (or Obtained)?
        3. 5.2.3 Using VIDs and PIDs During Development
    7. 6 Getting Started: Evaluating MSP430 USB
      1. 6.1 Software Development Environments
      2. 6.2 F5529 LaunchPad Development Kit
      3. 6.3 MSP430F5529 USB Experimenter's Board
      4. 6.4 FET Target Boards
    8. 7 More Information
  2.   A USB Glossary
  3.   Revision History

4.3.2 Choosing a Frequency

A wide range of frequencies is possible, because the USB PLL has a very flexible programmable input divider. Each MSP430 header file contains predefined constants for 43 possible frequencies, and many more are possible. (The pre-defined ones are of the format USBPLL_SETCLK_xx_yy, where xx_yy is frequency-specific.)

As shown in Section 4.3.1, each clock source is subject to a frequency range.

There are two considerations in frequency selection:

  • Lower-frequency crystals or resonators consume less power than higher ones. (See the device data sheet power consumption values for XT2.)
  • If using the USB BSL for factory programming of the MSP430 device, only 4, 8, 12, and 24 MHz are auto-recognized by the BSL. See Section 3.6.

USB-equipped MSP430 boards from TI usually use a 4-MHz ceramic resonator that meets USB precision requirements. Being the lowest-frequency crystal possible, these have the advantage of minimizing power consumption. 4 MHz is also auto-detected by the on-chip BSL.