Hi Yang..
If you look at the ATm128 datasheet over the Reset line you will find no reason why the mentioned thing should occur…
A badly designed power supply comes to mind … try adding a large capacitor to your +5V and at least 100nF to Reset ..
Regards
Lasse Madsen
-----Original
Message-----
From: Yang Wang
[mailto:yang_w2000@hotmail.com]
Sent: 27. august 2004 20:25
To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] Problem with
Atmega128 reset line
Hi all,
Can we connect the reset line and +5V line with a
1k pull-up
resistor, to keep the reset line high? Out of the
8 circuit boards
with the same schematics I am building, 6 of them
work in this way,
while the other two do not. For these two
problematic ones, the reset
line is always jumping between 2.1V and 4.7V, not
stable at all.
I feel like this 1k pull-up resistor setup should
work for keeping
the reset high, but I cannot find out why the
reset line is not
stable when it is connecting to +5V by the 1k
resistor. Or am I
wrong, and do I have to connect the reset line
with +5V directly?
Thanks a lot!
Yang