Re: [avr-chat] AVR do not restart after ISP programming

[Clemens Koller]

> Tonight, I replaced the bad 74HC244 with a new Philips 74HC244.
>
> The programmer works again, then I program the avr for about 5 times, it 
> goes wrong again.

Well, can you just verify all the little stuff, more in detail,
step by step, with the datasheets and some measurement equipment:

- check 3.3V versus 5V voltage levels. Not all 74xx244 can handle all voltages.
- floating inputs
- signal timing
- wrong signaling on the parallel port due to a software problem.
- maximum cable length, blocking capacitors, shielding, grounding
- ...

If you put your schematics of your programmer and connection to the avr
to some webpage, somebody might have a look and compare with working hardware.

> I think my programmer's hardware or the parallel port may have some 
> problems.

Then you should verify the signals of your parallel port with an oscilloscope.
I've seen some crappy parallel ports with only about 3.1Volts and some
100Ohms serial resistance. This isn't really a problem, if your circuits
are able to deal with it.

Regards,
--
Clemens Koller
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