How to check if a microcontroller is broken?

peekel Gast #885333
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Hi all,

I know it's a German forum so sorry for the English post. I'm in the 
learning period of German I can read it roughly but can't write.

Now I'm using atmega128 to do a project. Before the uC worked totally 
okay, however from this week it just stops working. I dont know what 
went wrong so I  used a simple method to check it, by which I attached a 
LED to the I/O port.

My circuit is truely simple, connect the PORTB.1 with a 470ohm resistor 
and the longer end of the LED, the shorter end of the LED was connected 
to the GND. I use 5V Vcc and JTAGICE.

my program is like this:

.INCLUDE "m128def.inc"


.CSEG
.ORG 0x00
  RJMP main

main:

  ldi r16, low(ramend)
  out spl, r16
  ldi r16, high(ramend)
  out sph, r16

repeat:

        ldi r16,0x01
  out ddrb,r16

  ldi r16,0x01
  out portb,r16

    jmp repeat



After all the uC didnt work any more, I was wondering if the 
microcontroller is broken. So I checked the voltage between Vcc and GND, 
and it is okay. So now I'm in no where. Could anyone tell me how to 
check if the microcontroller is broken? Dank!
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Bernhard Gast #885355
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Another good method is to put one PORT into output mode (using the DDR), 
and then give it some pattern like 0b10101010. Then just measure with a 
voltmeter, if you can see this pattern on the used port.
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peekel Gast #885375
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Thank Bernhard for the hint, I just did what u suggested, set the DDRB 
as 0xff, and PORTB as 0b10101010, and measure the voltage between each 
pin and GND, but I didnt see any pattern coming out, all the voltages 
stay constant which arounds zero.
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peekel Gast #885400
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hi, otto, the fuse is staying as it was before, I didnt change it. I 
think it should be no problem. Now I think I really have some problem 
with either the microcontroller or the JTAG, but dont know where to 
start to fix it.
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