53 lines
1.6 KiB
TeX
53 lines
1.6 KiB
TeX
\documentclass[../Diplomschrift.tex]{subfiles}
|
|
\begin{document}
|
|
|
|
\part{A short introduction to VHDL}
|
|
|
|
Designing a processor is a big task, and it's easiest to start very small. With software projects, this is usually in the form of a ``Hello World'' program - we will be designing a hardware equivalent of this.
|
|
|
|
\section{Prerequisites}
|
|
|
|
Other than a text editor, the following Free Software packages have to be installed:
|
|
|
|
\begin{savenotes}
|
|
\begin{description}
|
|
\item[\texttt{ghdl}\footnote{\url{https://github.com/ghdl/ghdl}}] to compile and simulate the design
|
|
\item[\texttt{gtkwave}\footnote{\url{http://gtkwave.sourceforge.net/}}] to view the generated waveform files
|
|
\item[GNU \texttt{make}] to coordinate simulating designs, compiling firmware and generating images
|
|
\item[python] for helper scripts
|
|
\end{description}
|
|
\end{savenotes}
|
|
|
|
\section{Creating a design}
|
|
|
|
A simple starting design is a D flip flop:
|
|
|
|
\def\svgwidth{2cm}
|
|
\input{d_flip_flop.pdf_tex}
|
|
|
|
The following VHDL code describes the device:
|
|
|
|
\lstinputlisting[title=\texttt{flipflop.vhd}]{vhdl/flipflop.vhd}
|
|
|
|
In order to test this design, a test bench has to be created:
|
|
|
|
\lstinputlisting[title=\texttt{flipflop\_tb.vhd}]{vhdl/flipflop_tb.vhd}
|
|
|
|
\section{Simulating a design}
|
|
|
|
\begin{lstlisting}[style=default,language=sh]
|
|
# analyze the design files
|
|
ghdl -a *.vhd
|
|
# elaborate the test bench entity
|
|
ghdl -e flipflop_tb
|
|
# run the test bench, saving the signal trace to a GHW file
|
|
ghdl -r flipflop_tb --wave=flipflop_tb.ghw
|
|
# open the trace with gtkwave
|
|
gtkwave flipflop_tb.ghw
|
|
\end{lstlisting}
|
|
|
|
\begin{center}
|
|
\includegraphics[width=\textwidth]{flipflop_gtkwave.png}
|
|
\end{center}
|
|
\end{document}
|