Dajgoro wrote:
Well i didn't mean it would catch fire or something like that, i only meant that the chip would not work anymore, since someone said recommended time is 50-100ms, 3 second it at least 30x more. It will be more likely that the chip might get damaged if the reset line is held down for a minute like you said...
I once witnessed a malfunction where a 65C22 had 8 of its peripheral lines shorted. The chip got hot enough to burn my finger... and yet it worked fine after the short was removed and everything cooled down. Admittedly that's not an exact parallel to an NMOS '02, but it does lend support to my view that, in regard to heat, these chips are not easy to kill. (Heck, they bake 'em in ovens during manufacture, don't forget!) So, the next question is: how long does it take for a chip to get that hot? Even in the rather severe malfunction I observed, the power dissipated would only be a few watts. And, the 40-pin plastic DIP package and its socket have significant thermal mass as well as some heat-sinking ability. So: although it's only a "guesstimate," I find it unlikely that the chip could achieve truly destructive temperatures in anything less than several seconds. We can bracket that amount widely: on one side with our cautious engineer in the 70's saying 50-100 ms, seeking to avoid damage; and, on the other side, with you and Ed and our other 6502.org experimenters, who ought to tread harshly in attempting to confirm that damage can be done! That latter point is what led me to suggest one minute.
On a different tack, it occurs to me that the 50-100 ms figure may be quoted on the low side not for fear of toasting the cpu but simply in order to minimize the burden on the 5 volt power supply, which would be in its power-up sequence during the time RST is asserted. Ie, the power supply might fail to wake up properly.
-- Jeff
