\documentclass{minimal}
\pagestyle{empty}

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

\begin{document}

\begin{psmatrix}[mnode=oval, colsep=3cm, rowsep=3cm]
[name=add]{\shortstack{\textbf{ADD}}} & &
[name=sub]{\shortstack{\textbf{SUB}}} \\
%
[mnode=R,name=res]{sys\_res\_n} &
[name=idle]{\shortstack{\textbf{idle}}}\\
%
[name=mul]{\shortstack{\textbf{MUL}}} & &
[name=div]{\shortstack{\textbf{DIV}}} \\
\end{psmatrix}

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

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

\ncarc[arcangle=20]{idle}{add}\ncput*[npos=.50]{\shortstack{do\_calc$\uparrow$\\opc = ADD}}
\ncarc[arcangle=20]{add}{idle}

\ncarc[arcangle=20]{idle}{sub}\ncput*[npos=.50]{\shortstack{do\_calc$\uparrow$\\opc = SUB}}
\ncarc[arcangle=20]{sub}{idle}

\ncarc[arcangle=20]{idle}{mul}\ncput*[npos=.50]{\shortstack{do\_calc$\uparrow$\\opc = MUL}}
\ncarc[arcangle=20]{mul}{idle}

\ncarc[arcangle=20]{idle}{div}\ncput*[npos=.50]{\shortstack{do\_calc$\uparrow$\\opc = DIV}}
\ncarc[arcangle=20]{div}{idle}
\end{document}
