\begin{tikzpicture}

    \tline{real}{0};
    \tline{model}{2};

    \ttimeline{real}{8.5};
    \ttimeline{model}{8.5};

    \tcaption{real}{Real system};
    \tcaption{model}{SystemC model};

    \tskip{real}{.5};
    \tskip{model}{.5};

    \path (currentrealU) coordinate (endzooma);
    \tbox{real}{7}{\texttt{compute()}};
    \path (currentrealU) ++(-.04, 0) coordinate (endzoomb);
    \tstrongtick{real};
    \ttextarrowU{real}{\texttt{commit()}};

    \tstrongtick{model};
    \path (currentmodelL) ++(-.04, 0) coordinate(startzooma);
    \path (currentmodelL) ++( .04, 0) coordinate(startzoomb);
    \ttextarrowU{model}{\texttt{compute()}};
    \tskip{model}{.04};
    \tskiptext{model}{6.92}{\texttt{wait()}};
    \tskip{model}{.04};
    \tstrongtick{model};
    \ttextarrowU{model}{\texttt{commit()}};

    \path (startzoomb -| endzoomb) coordinate (topright);
    \path (barycentric cs:startzoomb=.5,endzooma=.5) coordinate (tmpa);
    \path (barycentric cs:topright=.5,endzoomb=.5) coordinate (tmpb);
    \draw[very thin,color=black!70!white] (startzooma) -- (endzooma);
    \draw[very thin,color=black!70!white] (startzoomb) .. controls (tmpa) and (tmpb) .. (endzoomb);

\end{tikzpicture}

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