I am not an expert in assembly language so can someone help me please in solving this problem. I am simulating currently in proteus and having stack underflow error when button on PortA.0 is pressed/pulled low. The second error is for writing data to EEPROM location 0. The error says CPD bit in configuration word is not set.

My configuration word in my code is :
Code:
	__Config _XT_OSC & _WDT_OFF & _PWRTE_ON & _MCLRE_OFF & _BODEN & _CP & _CPD

The following is my ISR routine.

PIC->16F676

There are 4 output pins, PortC.0/3/4/5. The ISR routine is suppose to check if Button on PortA.0 is pressed then if all outputs are low then pull all of them high and if any one of them is high, then pull all of them low and wait for the button to be released. Also write the action taken on the outputs to the eeprom.

The code is also incrementing 4 byte size variables i,j,k,l to reach the value stored in p (which is 150). ISR is for TIMER0 interrupt only.

Code:
ISR:
asm
;CONTEXT SAVING CODE HERE

T0Overflow
       btfss     INTCON, T0IF    ; check if timer overflow flag
	Goto	EndInt

; PBP version
;		if i<p then i=i+1
;		if j<p then j=j+1
;		if k<p then k=k+1
;		if L<p then L=L+1

	movlw	_i
	bcf		STATUS,Z
	xorwf	_p,w                   ; p is a PBP variable and a constant with value 150. (P CON 150)
	btfss	STATUS,Z
	incf		_i

	movlw	_j
	bcf		STATUS,Z
	xorwf	_p,w
	btfss	STATUS,Z
	incf		_j

	movlw	_k
	bcf		STATUS,Z
	xorwf	_p,w
	btfss	STATUS,Z
	incf		_k

	movlw	_l
	bcf		STATUS,Z
	xorwf	_p,w
	btfss	STATUS,Z
	incf		_l

	btfsc	PORTA,0   ; Button Pressed?
	Goto Finish

	btfsc	PORTC,0
	Goto	Putlow       ; If it is high then pull all outputs low, goto Pull Low
	btfsc	PORTC,3
	Goto	Putlow
	btfsc	PORTC,4
	Goto	Putlow	
	btfsc	PORTC,5
	Goto	Putlow

; If none is high then put all outputs high
	bsf		PORTC,0
	bsf		PORTC,3
	bsf		PORTC,4
	bsf		PORTC,5

; Writing above states to EEPROM

	bsf		STATUS,RP0		; Jump tp BANK1
	
	clrf		EEADR
	movlw	1
	movwf	EEDATA
	Call		SaveVal
	
	movlw	1
	movwf	EEADR
	movwf	EEDATA
	Call		SaveVal

	movlw	2
	movwf	EEADR
	movlw	1
	movwf	EEDATA
	Call		SaveVal

	movlw	3
	movwf	EEADR
	movlw	1
	movwf	EEDATA
	Call		SaveVal

	bcf		STATUS,RP0	; Jump to BANK0
	Goto Skipp

; PBP version
;		If Sw1=0 then
;				if (PortC.0=0) then
;					if (PortC.3=0) then
;						if (PortC.4=0) then
;							if (PortC.5=0) then
;								High rel1 : High rel2 : High rel3 : High rel4
;								write 0,1 : write 1,1 : write 2,1 : Write 3,1
;								goto skipp
;							endif
;						endif
;					endif
;				endif
;				Low Rel1 : Low Rel2 : Low Rel3 : Low Rel4
;				write 0,0 : write 1,0 : write 2,0 : write 3,0
;                Endif
;skipp:
;                While PortA.0=0 : Pause 50 : Wend


SaveVal
		bsf		EECON1,WREN
		bcf		INTCON,GIE
		movlw	0x55
		movwf	EECON2
		movlw	0xAA
		movwf	EECON2
		bsf		EECON1,WR
		btfsc	EECON1,WR
		Goto	$-1
		bsf		INTCON,GIE
		RETURN

Putlow
	bcf		PORTC,0
	bcf		PORTC,3
	bcf		PORTC,4
	bcf		PORTC,5

; Writing above states to EEPROM

	bsf		STATUS,RP0
	clrf		EEADR          ; set eeprom address location - 0 in this case
	clrf		EEDATA        ; fill data in this register - 0 in this case
	Call		SaveVal        ; save it

	movlw	1
	movwf	EEADR
	clrf		EEDATA
	Call		SaveVal

	movlw	2
	movwf	EEADR
	clrf		EEDATA
	Call		SaveVal

	movlw	3
	movwf	EEADR
	clrf		EEDATA
	Call		SaveVal

	bcf		STATUS,RP0

Skipp
	btfss	PORTA,0     ; button released?
	GOTO	Skipp

Finish
       bcf		INTCON,T0IF
       clrf		TMR0

EndInt
CONTEXT RESTORE CODE
endasm
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