Hi Mo,

Theoretically speaking, the RC reset circuit is all you need to get a power-on reset. This is what all of the data sheets tell you. Of course, they're speaking of the ideal case. In practice however, these RC reset circuits are so unreliable, for so many possible reasons, I would strongly urge you to incorporate a reset supervisor IC into your circuit. Especially if you are working with any kind of prototype or kluged circuit board, the RC circuit becomes prohibitively unreliable. It's a very inexpensive addition to your circuit and I promise you that the only regret you will have is that you didn't incorporate one sooner.