Intermittent code cannot run

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

Code:

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

Quote:

Originally Posted by Pic2008

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

Code:

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

______

Actually I have other code after the LOW led. After many trial and error, if i remove intcon then this problem will not occur.
But this is not the solution because I need the interrupt to enable for it to increment the enc_counter.

Calling PBP library routines from ASM interrupt handlers, is generally not a good idea.

The commands will overwrite PBP's system variables in the middle of working on another command in the main program. The effects are completely unpredictable.

In your case, the only system var used by PAUSEUSL is R0. So if you save and restore the R0 Word variable much like psave and ssave, it should work better.
<br>