MP sim debugging prob...

Hello,
I am new to pic & MPLAB, i tried a piece of code:

LIST P=PIC18F458, F=INHX32, MM=OFF, N=0, ST=OFF, R=HEX
#include P18F458.INC
CONFIG OSC=HS, OSCS=OFF
CONFIG WDT=OFF

CONFIG BORV=45, PWRT=ON, BOR=ON


CONFIG DEBUG=OFF, LVP=OFF, STVR=OFF
portb equ 0X0F81

ORG 0

movlw 55h;
movwf portb
repeat
comf portb,f
goto repeat
END



it was build successfuly ,,but when i try to debug using MP SIM , & while using step-into & WATCH window (in which i have added port b), there seems to be no change in port b value,, i.e the watch windows shows the value of port b remain at 0x00.. so what could be the prob ?
thanks

PortB is still set to input. You need to write 0x00 to TRISB to make it output.

Mike.