what might be wrong

[t.man]

I have this program for blinking LED...but that's not what happens. LED is always ON. is the delay too small?

whats the problem?

.include "m8def.inc"

	rjmp	RESET		;reset handle


;* Long delay 

;* Register variables

	.def  T1      = r1
	.def  T2      = r2
	.def  temp    = r19

;* Code
	    
longDelay:      
	clr   T1		;T1 used as delay 2nd count
	clr   T2		;T2 used as delay 3d count
delay_1:    
	dec   T2
	brne  delay_1            
	dec   T1
	brne  delay_1           
	dec   temp		
	brne  delay_1		
	ret                     


;* Resets the data direction register D

;* Defines

	.equ  led   = 6		;LED at PD6

;* Code

RESET:
	sbi   DDRD, led		;connect LED to PORTD pin 6
	    

;* Main program

;* This part will let the LED go on and off by w

;* Register variables

	.equ  w   =  10 	;enter delaytime w

flash: 
	sbi   PORTD, led	;LED on
	ldi   temp, w		;w sec delay           
	rcall longDelay             
	cbi   PORTD, led	;LED off            
	ldi   temp, w		;w sec delay
	rcall longDelay
	rjmp  flash		;another run

the program is running on mega8 using a 6.144MHz crystal.

 

[eblc1388]

whats the problem?

You'll need to add the code to initialize the STACK Pointer or else the stack pointer initialise to all zero after reset. See the following code:

.include "m8def.inc"

	rjmp	RESET		;reset handle

;* Code

RESET:
[color=red][b]        ldi   temp,HIGH(RAMEND)    ; get high byte of end of memory address
        out   SPH,temp
        ldi   temp,LOW(RAMEND)     ; get low byte of end of memory address
        out   SPL,temp
[/b][/color]
	sbi   DDRD, led		;connect LED to PORTD pin 6
	    

;* Main program

;* This part will let the LED go on and off by w