%%% outline
%-------------------------------------------------------------------------
\begin{tikzpicture}
\tikzstyle{opt}=[draw,minimum height=2em,minimum width=4em,rounded corners=2pt,thick]

\node[circle,minimum size=2em,draw,fill=red!20] (x1) at (0,0) {\small\bfnew{X}};
\node[circle,minimum size=2em,draw,fill=red!20] (x2) at (0,4em) {\small\bfnew{X}};
\node[circle,minimum size=2em,draw,fill=red!20] (x3) at (0,-5em) {\small\bfnew{X}};

\node[anchor=west,opt,fill=yellow!20] (unary1) at ([xshift=3em]x1.east){\small\bfnew{Unary}};
\node[anchor=west,opt,fill=yellow!20] (unary2) at ([xshift=3em]x2.east){\small\bfnew{Unary}};

\node[opt,fill=blue!20] (binary1) at (12em,2em){\small\bfnew{Binary}};
\node[opt,fill=blue!20] (binary2) at (25em,-1.5em){\small\bfnew{Binary}};
\node[anchor=west,opt,fill=yellow!20] (unary3) at ([xshift=3em]binary1.east){\small\bfnew{Unary}};
\node[anchor=west,opt,fill=yellow!20] (unary4) at ([xshift=16em]x3.east){\small\bfnew{Unary}};


\draw[-latex,very thick] (x1.0) -- (unary1.180);
\draw[-latex,very thick] (x2.0) -- (unary2.180);
\draw[-latex,very thick] (x3.0) -- (unary4.180);
\draw[-latex,very thick] (unary1.0) -- ([yshift=-0.2em]binary1.180);
\draw[-latex,very thick] (unary2.0) -- ([yshift=0.2em]binary1.180);
\draw[-latex,very thick] (binary1.0) -- (unary3.180);
\draw[-latex,very thick] (unary3.0) -- ([yshift=0.2em]binary2.180);
\draw[-latex,very thick] (unary4.0) -- ([yshift=-0.2em]binary2.180);

\begin{pgfonlayer}{background}
\node[draw=lightgray,fill=lightgray!50,rounded corners=2pt,inner sep=8pt][fit=(x2)(x1)(binary1)]{};
\end{pgfonlayer}
\node[anchor=south] at ([yshift=1em]binary1.north){\small\bfnew{Core Unit}};
\end{tikzpicture}