You might try looking at Darrel's sample here: http://www.picbasic.co.uk/forum/show...0434#post80434

ASM ; 18F13K50/14K50 Only 12mhz crystal can be used for USB
__CONFIG _CONFIG1L, _CPUDIV_NOCLKDIV_1L & _USBDIV_OFF_1L
__CONFIG _CONFIG1H, _FOSC_HS_1H & _PLLEN_ON_1H & _PCLKEN_ON_1H & _FCMEN_OFF_1H & _IESO_OFF_1H
ENDASM

DEFINE OSC 48