gistfile1.tex

\documentclass[]{beamer}

\usepackage[T1]{fontenc} 
\usepackage[brazil]{babel}  
\usepackage[utf8]{inputenc}
\usepackage{ifpdf}
\usepackage{bytefield}

\begin{document}

\begin{frame}[fragile]
  Mux
  \\[2em]
  \begin{bytefield}[bitwidth=2em]{16}
    \bitheader[endianness=little]{0,3,7,11,15} \\
    \bitbox{4}{size}\bitbox{1}{\tiny type}\bitbox{8}{[size-8]message}
  \end{bytefield}
\end{frame}

\end{document}