\documentclass{minimal}
\pagestyle{empty}

\usepackage{pstricks}
\usepackage{pst-node}

\begin{document}

\begin{psmatrix}[mnode=oval, colsep=3cm, rowsep=3cm]
[mnode=R,name=res]{sys\_res\_n} &
[name=rwb]{\shortstack{\textbf{rwbyte}\\s++;}} \\
%
[name=idle]{\shortstack{\textbf{idle}\\z:=0; s:=0;}} &
[name=zeile]{\shortstack{\textbf{nzeile}\\z++;\\s:=0;}} \\
\end{psmatrix}

\psset{arrows=->, shortput=nab}

\ncline[linestyle=dotted]{res}{idle}

\ncarc[arcangle=30]{idle}{zeile}\ncput*[npos=.50]{\shortstack{rx\_new$\uparrow$
\&\&\\rx\_data='\textbackslash 0'}}
\ncarc[arcangle=0]{idle}{zeile}\ncput*[npos=.50]{btn$\uparrow$}

\ncarc[arcangle=40]{zeile}{idle}\ncput*[npos=.50]{$z>50$}

\ncarc[arcangle=25]{zeile}{rwb}\ncput*[npos=.40]{$z\le50$}
\ncarc[arcangle=25]{rwb}{zeile}\ncput*[npos=.40]{$s>71$}

\nccircle[angleA=0]{rwb}{.70cm}\ncput*[npos=0.5]{$s\le71$}
\end{document}
