Ich habs zwar nicht getestet aber so müsste theoretisch pin1 von Port a pwm-mäßg bei 50% toggeln.

Code:
.include <m8535def.inc> 

.org 0x0000 
rjmp init

.org OVF0addr 
rjmp ovf

.org OC0addr 
rjmp ocr

init:
ldi R26, 0b00000000 

ldi R16, HIGH(RAMEND) 
out SPH, R16 

ldi R16, LOW(RAMEND) 
out SPL, R16 

ldi R16, 0x7b 
out TCCR0, R16 

ldi R16, 0x03
out TIMSK, R16 

ldi R17, 0x7f
out OCR0, R17 

ldi DDRA, 0x01

sei 

mainloop:
rjmp mainloop

ovf:
ldi r16, 0x01
out PORTA, r16
reti

ocr:
ldi r16, 0x00
out PORTA, r16
reti
MFG,
Alex