PIC32MX Oscillator - USB PLL

USB PLL Configuration

usb.PNG

The USB Clock can be derived from the 8 MHz internal FRC Oscillator, 48 MHz POSC, or the USB PLL. For normal operation, the USB module requires an accurate 48 MHz clock.

The USB PLL input divider must be configured to provide 4 MHz to the multiplier. This divider is controlled by the UPLLIDIV setting with the following options:
÷1, ÷2, ÷3, ÷4, ÷5, ÷6, ÷10, ÷12

The internal 8 MHz FRC Oscillator is available as a clock source to detect any USB activity during USB Suspend mode and bring the module out of the Suspend mode. This lowers power consumption while in suspend mode.

The default USB PLL input divider and USB PLL enable can be configured at program time only. The USB clock source can be configured with the following MPLAB® Harmony function at run-time.

// if POSC = 12, default USB PLL input divide = 3
#pragma config UPLLIDIV = DIV_3
// default USB PLL enabled
#pragma config UPLLEN = ON
...
// following functions select POSC or FRC as input for the USB clock at run-time
PLIB_OSC_UsbClockSourceSelect(OSC_ID_0, SYS_OSC_USBCLK_PRIMARY);
// use for lower power during Suspend
PLIB_OSC_UsbClockSourceSelect(OSC_ID_0, SYS_OSC_USBCLK_FRC);

20th Annual
Microchip MASTERs Conference 2016
Register now - Deadline: July 29

JW Marriott Desert Ridge Resort-Phoenix, AZ

© 2016 Microchip Technology, Inc.
Information contained on this site regarding device applications and the like is provided only for your convenience and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. MICROCHIP MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS FOR PURPOSE. Microchip disclaims all liability arising from this information and its use. Use of Microchip devices in life support and/or safety applications is entirely at the buyer's risk, and the buyer agrees to defend, indemnify and hold harmless Microchip from any and all damages, claims, suits, or expenses resulting from such use. No licenses are conveyed, implicitly or otherwise, under any Microchip intellectual property rights.