Hi Rob:
if pic18f4550 use 16Mhz crystal , how to set 'Config1L to get precise output timing ?

'Config1L
' Full-speed USB Clock Source Selection: Clock Source from 96MHz PLL/2
' CPU System Clock Postscaler: Prescaler Divide by 5 for 20MHz Crystal
' 96MHz Prescaler: Divide by 5 (20MHz Input)
@ __CONFIG _CONFIG1L, _USBDIV_2_1L & _CPUDIV_OSC1_PLL2_1L & _PLLDIV_5_1L

'Config1H
'Oscillator: HS oscillator, PLL enabled, HS used by USB
'Fail-Safe Clock Monitor Enable: Enabled
'Internal External Switch Over Mode: Disabled
@ __CONFIG _CONFIG1H, _FOSC_HSPLL_HS_1H & _FCMEM_ON_1H & _IESO_OFF_1H

thanks , regards
Lee