[walid el masry]

اعتذر عن كتابتي بالانجليزية و لكني وجدت انها اسلم طريقة لايضاح المشكله

hi every body

i want to build a program which uses the external interrupt , TMR0 and TMR1 over flow interrupts
but unfortunately there is a stack over flow error occurred and i noted that

it didn't happen when i never initialize the value for the OPTION_REG
register

1st i tested the code of the TMR1 over flow interrupt to make a 1sec delay and it works, every 1 sec it invert the value of the PORTB so that LED flashes

then when trying to test initialization to use the TMR0 over flow interrupt the
stack over flow error occurred

here is the code i wrote and i hope i was clear

    LIST P=16F876
    #INCLUDE<P16F876.INC>
    __CONFIG _CP_OFF&_LVP_OFF&_BODEN_OFF&_PWRTE_ON&_WDT_OFF&_XT_OSC
;************declare variables************
    CBLOCK 0X20
W_TEMP
STATUS_TEMP
PCLATH_TEMP
TMR1_counter
    ENDC
;************Reset vector************
    ORG 0X00
    GOTO INIT     
;*****************Interrupt vector**************************
    ORG 0X04 
;******************Interrup subrutine*****************
;***********************
; code from datasheet 14.12 Context Saving During Interrupts P154
MOVWF W_TEMP ;Copy W to TEMP register
SWAPF STATUS,W ;Swap status to be saved into W
CLRF STATUS ;bank 0, regardless of current bank, Clears IRP,RP1,RP0
MOVWF STATUS_TEMP ;Save status to bank zero STATUS_TEMP register
MOVF PCLATH, W ;Only required if using pages 1, 2 and/or 3
MOVWF PCLATH_TEMP ;Save PCLATH into W
CLRF PCLATH ;Page zero, regardless of current page
;***********************
    BTFSS   PIR1,TMR1IF; is the interrupt accured is for TIMER0 or not ?
    GOTO    ENDI;NO
    BCF     PIR1,TMR1IF;YES
    DECF    TMR1_counter,f; decrement the counter
    btfss   STATUS,Z; test if  counter reaches the end - 1 second have just passed
    GOTO    ENDI;NO
    MOVLW   D'1';YES
    MOVWF   TMR1_counter; re-intiate counter value
;***********************Code Executed every second*************************
ONE
    MOVLW 0X00
    XORWF PORTB,W
    BTFSS STATUS,Z
    GOTO ZERO;NO
    MOVLW 0XFF;YES
    MOVWF PORTB
    GOTO ENDI
ZERO
    MOVLW 0X00
    MOVWF PORTB
;***********************every time when leaving interrupt do this*************************
ENDI
;***********************
; code from datasheet 14.12 Context Saving During Interrupts P154
MOVF PCLATH_TEMP, W ;Restore PCLATH
MOVWF PCLATH ;Move W into PCLATH
SWAPF STATUS_TEMP,W ;Swap STATUS_TEMP register into W
;(sets bank to original state)
MOVWF STATUS ;Move W into STATUS register
SWAPF W_TEMP,F ;Swap W_TEMP
SWAPF W_TEMP,W ;Swap W_TEMP into W
;***********************
BSF INTCON,GIE
BSF INTCON,PEIE
BSF STATUS,RP0
BSF PIE1,TMR1IE
BCF STATUS,RP0
    RETFIE; end of interrupt subrutine
;*****************Chip initialize**************************
INIT
BSF STATUS,RP0;goto Bank1
;******************
;initialize PORTs type and direction
MOVLW 0X06
MOVWF ADCON1;PORTA is digital i/o
MOVLW 0X00
MOVWF TRISA;PORTA is output
MOVWF TRISC;PORTC is output
MOVLW 0X01
MOVWF TRISB;PORTB is output exept 1st pin
;******************
MOVLW B'01000111'
;MOVWF OPTION_REG;TMR0 Prescaler Rate 1 : 256 & External interrupt on rising edge
;******************
MOVLW B'11110000';clear TMR0 & External flag
MOVWF INTCON;Enables all unmasked interrupts & unmasked peripheral interrupts & TMR0 & External interrupts
;******************
MOVLW B'00000001'
MOVWF PIE1;Enables the TMR1 overflow interrupt
;******************
BCF STATUS,RP0;goto Bank0
;******************
CLRF TMR0
CLRF TMR1L
CLRF TMR1H
;******************
MOVLW B'00000000'
MOVWF PIR1;clear TMR1 flag
;******************
MOVLW B'00110001'
MOVWF T1CON;TMR1 Prescaler Rate 1 : 8 & Enables Timer1
;******************
;initialize PORTs and variables value
CLRF PORTA
CLRF PORTB
CLRF PORTC
MOVLW   D'1'
MOVWF   TMR1_counter 
;******************
;************************main program********************           
START   
    GOTO START
    END

note that ones i remove the ";" beside the "MOVWF OPTION_REG"
the stack over flow occurs

and this is the test circuit