Intermittent code cannot run

[duncan303]

When I first power ON the PIC16F877, sometimes I don't see the LED turn ON, which means my code not running. Anything wrong?

include "modedefs.bas"

define osc 20

asm
 device  pic16f877,hs_osc,BOD_OFF,wdt_off,pwrt_on,protect_off  
endasm

clear
    
    ADCON1=%00000111      'PIC16F877 turn off analog comparator,        
    OPTION_REG.7 = 0     'enable internal pull up GPPU
    OPTION_REG.6 = 0     'falling edge INT
    TRISB = %00010001         
'*********************** ASSEMBLY INTERUPT VARIABLES ***********************
wsave   var     byte $20 system
wsave1  var     byte $a0 system  ' Necessary for devices with RAM in bank1
wsave2  var     byte $120 system ' Necessary for devices with RAM in bank2
wsave3  var     byte $1a0 system ' Necessary for devices with RAM in bank3
ssave   var     byte bank0 system
psave   var     byte bank0 system     

a var byte
b var byte
c var byte
d var byte
task var byte
enc_counter var word
RxD             var PORTC.7
TxD             var PORTC.6
led var PORTE.2

goto start			'skip over interupt handler

'*********************** ASSEMBLY INTERUPT HANDLER *************************

define  INTHAND myint
Asm
       
myint 
  	
	; Save W, STATUS and PCLATH registers, if not done previously
        ;movwf   wsave
        ;swapf   STATUS, W
        ;clrf    STATUS
        ;movwf   ssave
        ;movf    PCLATH, W
       ; movwf   psave  
         
        movlw   high 100      ; Wait 100us to debounce encoder
        movwf   R0 + 1
        movlw   low 500
        call    PAUSEUSL   
       
        incf    _d, w         ;d dummy counter
        nop
        movwf   _d
        
        
        incfsz  _enc_counter,W      ; Add one to low byte
        decf    _enc_counter+1,F    ; No carry (negates next step)
        incf    _enc_counter+1,F    ; Add one to high byte
        movwf   _enc_counter        ; Store updated low byte back.
        iorwf   _enc_counter+1,W    ; Set Z flag
		
	  
	   bsf     _led		    ;turn on led   


        ; Restore saved registers      
        
        movf    psave, W
        movwf   PCLATH
        swapf   ssave, W
        movwf   STATUS
        swapf   wsave, F
        swapf   wsave, W
      
        bcf     INTCON, INTF
        bcf     INTCON, RBIF		  ; Clear the Interupt Flag
        RETFIE                 	  	  ; Return from interrupt
endasm


start:
    intcon=%10011000     ' enable int
    a= 1
   
    high led
    pause 500
    low led

did you want the led to flash or just come on only once? maybe a goto (somewhere) at the end of the start: routine to create a loop somewhere otherwise the program just ends.

also always good practice to place END at the very end of all programs.

As for the intermittent part try a pause somewhere near the begining of the prog to allow the pic to "settle"

HTH

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