multipart nodes anchors for dividers

Question

How can a node be positioned at the center/edge of a part in a multipart node using relative positioning?

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shapes.multipart}
\usetikzlibrary{positioning}
\begin{document}
\begin{tikzpicture}
\node[align=center,draw,shape=rectangle split,rectangle split horizontal,rectangle split parts=3, text width=2cm] (A) at (1.5,3) 
{one\nodepart{two}two\nodepart{three}three};
\node[draw,shape=circle] (E) at (2.7,1) {$E$};
\node[draw,shape=circle] (C) at (3.7,1) {$C$};
\end{tikzpicture}
\end{document}

This is the desired result:

Answer 1

You mean like this?

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shapes.multipart}
\usetikzlibrary{positioning}
\begin{document}
\begin{tikzpicture}
\node[align=center,draw,shape=rectangle split,rectangle split horizontal,rectangle split parts=3, text width=2cm] (A) at (1.5,3) 
{$m$\nodepart{two}$0 \ldots 0$\nodepart{three}$r$};
\node[draw,shape=circle] (E) [below=of A.two split south] {$E$};
\node[draw,shape=circle] (C) [below=of A.three south] {$C$};
\end{tikzpicture}
\end{document}

The TikZ manual version 2.10, page 453 displays the anchors for the vertical split rectangle. You have to reinterpret for the horizontal version.