AVR-Chat

Hi Guys,

Ive had two different boards lately give a lot of trouble, both had 
OUTPUTS on AVR chips connected directly to inputs on 74HC and 74LS 
logic chips. 

Looking at it with my scope, it appeared that the AVR was unable to 
pull the input on the logic chip completely low ? It would pull it to 
around 1 to 3 volts for a low output.

I did ensure that the pins were set up as OUTPUTS, nothing else 
weird. 

Both problems were solved by connecting 100k resistors from the input 
pins on the logic chips to ground.

Any ideas ? Im sure it will be obvious as soon as someone points out 
the obvious, but it's got me beat.

Cheers
Hein B
Andante Technology
Auckland
New Zealand.