![NXP Semiconductors MKL27Z128VFM4 Reference Manual Download Page 562](http://html1.mh-extra.com/html/nxp-semiconductors/mkl27z128vfm4/mkl27z128vfm4_reference-manual_1721847562.webp)
2. Enable the USB clock recovery tuning:
USB_CLK_RECOVER_CTRL[CLOCK_RECOVER_EN] = 1b
3. Choose the clock source of USB by configuring the muxes in the SIM. MCG HIRC
supplies the HIRC 48mhz clock by setting SIM_SOPT2[USBSRC] = 1b.
4. The USB clock source can be selected from the USB_CLKIN pad by setting
SIM_SOPT2[USBSRC] = 0b.
For chip-specific details, see the USB FS OTG controller clocking information in the
"Clock Distribution" chapter.
Device mode IRC48 operation
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
562
Freescale Semiconductor, Inc.