m-cin wrote:For many reasons (like noise resistance) it is wise not to leave any pin floated. For another reasons (like current limiting in case of unintended shortcuts or in/out circuit failure) it is wise to use pull-up/down resistors. In order to bypass unstable conditions at power-up it is good to add a capacitor to RST.
It may be that your circuit without any of the above works correct, but the probability of such event in noisy environment is rather low Please read here about problems with even simple relay switching...
Kind regards
M.