Hi Guys:
        Thanks for the info you gave me. It help me to solve my problem. I
managed to get the program working in the simulator.
        However, when I burn in the program into the PIC17C44, I could not get
the output from PORTD when I changed the input of PORTC!!! Strange! I
wonder if there's anything to do with my way of writing my program. I've
attached my program as a text file and another one is the error text.
        Also when I contact up the cct, I grounded both Vss, Vdd to 5V and a
external clock source(programmable one) to osc1. That's all. And, for
the input, it's to the switches.....the output, it's to the LEDS.
        That's all...

....."The journey of a thousand miles begins with a
small step in the right direction.".......

----------------------------
Name    : Koh Teik Siong
Email   : tsk196@soton.ac.uk
Tel     : +44 (01703) 766255
Address : Flat 4 Rm 19
          Beechmount House
          Beechmount Rd
          Bassett
          Southampton
          SO16 3JD
-----------------------------

;***********************************************************
;               DIGITAL TO ANALOG CONVERTER
;
;       This program converts the digital signal -128 to 127
;to give a output voltage of -10V to 10V. This is to control
;the voltage of the motor so that it can rotate the motor to
;the desire speed and position.
;
;***********************************************************

        list    P=17C44, r=hex



ddrc    equ     0x0110 ; I've also tried to use address 0x10
portc   equ     0x0111 ; I've also tried to use address 0x10
ddrd    equ     0x0112 ; I've also tried to use address 0x10
portd   equ     0x0113; I've also tried to use address 0x10
w       equ     0x000A
count   equ     0x0020

        ORG     0x0000
        GOTO    START

START
DELAY   macro   count
        VARIABLE I
I = 0
        WHILE I < count
I += 1
        ENDW
        ENDM

        CALL    INIT

LOOP    MOVLB   1
        movpf   portc,portd     ;GET DATA
        DELAY   100             ;O/P TO PORTD
        GOTO    LOOP            ;

INIT    MOVLB   1       ;MOVE TO BANK 1
        CLRF    portc,1 ;INIT PORTC
        setf    ddrc,1  ;PORTC IS I/P

        clrF    portd,1 ;INIT PORTD
        clrf    ddrd,1  ;PORTD IS O/P
        MOVLB   0       ;MOVE TO BANK 0
        RETURN
        END

Warning[202] C:\MPLAB\TUTOR\DAC.ASM 37 : Argument out of range.  Least
 significant bits used.
Message[302] C:\MPLAB\TUTOR\DAC.ASM 37 : Register in operand not in bank 0.
 Ensure that bank bits are correct.
Message[302] C:\MPLAB\TUTOR\DAC.ASM 42 : Register in operand not in bank 0.
 Ensure that bank bits are correct.
Message[302] C:\MPLAB\TUTOR\DAC.ASM 43 : Register in operand not in bank 0.
 Ensure that bank bits are correct.
Message[302] C:\MPLAB\TUTOR\DAC.ASM 45 : Register in operand not in bank 0.
 Ensure that bank bits are correct.
Message[302] C:\MPLAB\TUTOR\DAC.ASM 46 : Register in operand not in bank 0.
 Ensure that bank bits are correct.