Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/NXP Semiconductors/LPC13xx/SYSCON/USBCLKSEL#0x0
SEL=USB_PLL_OUT
USB clock source select
USB clock source
0 (USB_PLL_OUT): USB PLL out
1 (MAIN_CLOCK): Main clock
2 (RESERVED): Reserved
3 (RESERVED): Reserved
Reserved
https://github.com/cmsis-svd/cmsis-svd-data