Hi all,

I finally got my PIC programmer (El Cheapo) working so I thought I would
try my hand at a simple program.  I wrote a program to count from 0 to 255
and display the contents of the count register on portb.  I have a 10 LED
dip package connected to portb, two of the LEDs are not connected.  The
pause routine I put in is simply to allow me some time to view the contents
of portb.  I realize that the tris command is obsolete and not recommended
but I'm learning from a couple different books (Myke Predko's, and Easy
Pic'n) and using the tris command seemed to be the easiest solution for my
first program.  In MPLAB I set up the PIC using XT for the resonator, 4Mhz
for the speed, WDT disabled.  The program compiles and burn into memory
just fine but when I plug the chip into the circuit, nothing seems to
happen.  I am 99% sure I set up the circuit properly as I have checked and
re-checked all the connections at least 10 times.  I also stepped through
the program listed below in MPLAB and it seemed to execute properly.  Using
watch windows in MPLAB everything checked out.  As for the circuit, I
started out using a 330 Ohm dip package in series with the anode pins of
the LED dip package.  Next I tried tying the cathode pins of the LED
package to portb and the anode pins of the LEDs to 330 Ohm resistors.  No
LEDs turned on in either configurations.  Any help is greatly appreciated.

Sincerely,
Scott Pierce



;== Scott Pierce ================================================ 8/24/2002 ===
;
; Counts from 0 to 255 and displays contents on portb
;
;
;==============================================================================
;
        list    p=16f84a
        radix   hex
;
;==============================================================================
;
portb   equ     0x06
count   equ     0x0c
counti  equ     0x0d
countj  equ     0x0e
;
;==============================================================================
;
        org     0x00
;
;==============================================================================
;
start   movlw   0x00
        tris    portb   ;set portb to all outputs
        movlw   0xff    ;set portb high
        movwf   portb   ;set portb to all 0's
        clrf    counti  ;set counti to 0
        clrf    countj  ;set countj to 0
        clrf    count   ;set count  to 0
;
;==============================================================================
;
dispcnt movf    count,w ;move contents of count into work register
        movwf   portb   ;output contents of count to portb
        call    pause
        incf    count,f ;increment count by one, results stored in file reg
        goto    dispcnt ;start loop over again
;
;==============================================================================
;
pause   movlw   0x0f    ;set counter to 254
        movwf   counti  ;move work register to counti file register
loadj   movlw   0x0f    ;set countj to 255
        movwf   countj  ;move work register to countj file register
decj    decfsz  countj,f;decrement countj, if zero skip next instruction
        goto    decj    ;loop decj again until countj = 0
        decfsz  counti,f;decrement counti, if zero skip next instruction
        goto    loadj   ;loop loadj again until counti = 0
        return          ;when nested loops are done, return to dispcnt loop
;
;==============================================================================
;
        end
;
;==============================================================================

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