Yes, there's initialization routine just before above code.

;STACK POINTER INITIALIZATION
	LDI  R30,LOW(0x10FF)
	OUT  SPL,R30
	LDI  R30,HIGH(0x10FF)
	OUT  SPH,R30

;DATA STACK POINTER INITIALIZATION
	LDI  R28,LOW(0x500)
	LDI  R29,HIGH(0x500)

	JMP  _main

	.ESEG
	.ORG 0
	.DB  0 ; FIRST EEPROM LOCATION NOT USED, SEE ATMEL ERRATA SHEETS

	.DSEG
	.ORG 0x500


--

QH Hong.

qhhong wrote:
> I have just started to study the AVR a week ago.
> The eight LEDs and registors are connected between the VCC and
> ATMEGA128 PORTB.
> 
> I found that some CodeVision C programs does not work as I expected.
> After careful examination of the codes, I can simplify the problem to
> the following Assembler coding.  (PORTD.0 is connected to the
> chattering switch)
> 
> 	.CSEG
> _main:
> ;       8 	PORTB=0xff;
> 	LDI  R30,LOW(255)
> 	OUT  0x18,R30
> ;       9 	DDRB=0xFF;
> 	OUT  0x17,R30
> ;      10
> ;      11 	PORTD=0x00;
> 	CLR  R30
> 	OUT  0x12,R30
> ;      12 	DDRD&=0xFE;
> 	CBI  0x11,0
> ;      13
> 	;CALL __LSLB12 ;====> If commented OK!!!!! But uncommented??<===
> 	LDI  R30,LOW(5)
> 	OUT  0x18,R30
> _0x3:
> 	RJMP _0x3
> 
> __LSLB12:
>     RET
> 
> If I comment the CALL statement, the the LEDs light as I expected.
> But when I revive the CALL statement, the LEDs doesn't light at all!
> 
> I loaded this assembler to the AVRStudio simulator. But the simluator
> shows PORTB works as I expected irrespective of the CALL statement.
> 
> Where am I wrong?
> 

Did anybody initialize your stack pointer?

-- 

Tauno Voipio
tauno voipio (at) iki fi

I have just started to study the AVR a week ago.
The eight LEDs and registors are connected between the VCC and
ATMEGA128 PORTB.

I found that some CodeVision C programs does not work as I expected.
After careful examination of the codes, I can simplify the problem to
the following Assembler coding.  (PORTD.0 is connected to the
chattering switch)

	=2ECSEG
_main:
;       8 	PORTB=3D0xff;
	LDI  R30,LOW(255)
	OUT  0x18,R30
;       9 	DDRB=3D0xFF;
	OUT  0x17,R30
;      10
;      11 	PORTD=3D0x00;
	CLR  R30
	OUT  0x12,R30
;      12 	DDRD&=3D0xFE;
	CBI  0x11,0
;      13
	;CALL __LSLB12 ;=3D=3D=3D=3D> If commented OK!!!!! But uncommented??<=3D=
=3D=3D
	LDI  R30,LOW(5)
	OUT  0x18,R30
_0x3:
	RJMP _0x3

__LSLB12:
    RET

If I comment the CALL statement, the the LEDs light as I expected.
But when I revive the CALL statement, the LEDs doesn't light at all!

I loaded this assembler to the AVRStudio simulator. But the simluator
shows PORTB works as I expected irrespective of the CALL statement.

Where am I wrong?