The below works using the internal OSC for a test.
' PIC18F2550
DEFINE OSC 8
ASM
__CONFIG _CONFIG1L, _PLLDIV_1_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L
__CONFIG _CONFIG1H, _FOSC_INTOSCIO_EC_1H
__CONFIG _CONFIG2H, _WDT_OFF_2H & _WDTPS_512_2H
__CONFIG _CONFIG3H, _PBADEN_OFF_3H & _MCLRE_OFF_3H
__CONFIG _CONFIG4L, _LVP_OFF_4L
ENDASM

ADCON1 = %00001111
CMCON = 7
OSCCON = %01110000
TRISB = %00000000
START

LATB.2 = 1
PAUSE 250
LATB.2 = 0
PAUSE 250
GOTO START