5 files changed, 109 insertions, 3 deletions
diff --git a/manual/PRESENTATION_ExOth.tex b/manual/PRESENTATION_ExOth.tex
index 13ec3d19..64c4af72 100644
--- a/manual/PRESENTATION_ExOth.tex
+++ b/manual/PRESENTATION_ExOth.tex
@@ -23,10 +23,70 @@ This section contains 3 subsections:
 \subsectionpagesuffix
 \end{frame}
 
-\subsubsection{TBD}
+\begin{frame}{\subsecname}
+Yosys can also be used to investigate designs (or netlists created
+from other tools).
 
-\begin{frame}{\subsubsecname}
-TBD
+\begin{itemize}
+\item
+The selection mechanism (see slides ``Using Selections''), especially pattern such
+as {\tt \%ci} and {\tt \%co}, can be used to figure out how parts of the design
+are connected.
+
+\item
+Commands such as {\tt submod}, {\tt expose}, {\tt splice}, \dots can be used 
+to transform the design into an equivialent design that is easier to analyse.
+
+\item
+Commands such as {\tt eval} and {\tt sat} can be used to investigate the
+behavior of the circuit.
+\end{itemize}
+\end{frame}
+
+\begin{frame}[t, fragile]{Example: Reorganizing a module}
+\begin{columns}
+\column[t]{4cm}
+\lstinputlisting[basicstyle=\ttfamily\fontsize{6pt}{7pt}\selectfont, language=verilog]{PRESENTATION_ExOth/scrambler.v}
+\column[t]{7cm}
+\begin{lstlisting}[basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys, frame=single]
+read_verilog scrambler.v
+
+hierarchy; proc;;
+
+cd scrambler
+submod -name xorshift32 xs %c %ci %D \
+           %c %ci:+[D] %D %ci*:-$dff \
+           xs %co %ci %d
+\end{lstlisting}
+\end{columns}
+
+\hfil\includegraphics[width=11cm,trim=0 0cm 0 1.5cm]{PRESENTATION_ExOth/scrambler_p01.pdf}
+
+\hfil\includegraphics[width=11cm,trim=0 0cm 0 2cm]{PRESENTATION_ExOth/scrambler_p02.pdf}
+\end{frame}
+
+\begin{frame}[t, fragile]{Example: Analysis of circuit behavior}
+\begin{lstlisting}[basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
+> read_verilog scrambler.v
+> hierarchy; proc;; cd scrambler
+> submod -name xorshift32 xs %c %ci %D %c %ci:+[D] %D %ci*:-$dff xs %co %ci %d
+
+> cd xorshift32
+> rename n2 in
+> rename n1 out
+
+> eval -set in 1 -show out
+Eval result: \out = 270369.
+
+> eval -set in 270369 -show out
+Eval result: \out = 67634689.
+
+> sat -set out 632435482
+Signal Name                 Dec        Hex                                   Bin
+-------------------- ---------- ---------- -------------------------------------
+\in                   745495504   2c6f5bd0      00101100011011110101101111010000
+\out                  632435482   25b2331a      00100101101100100011001100011010
+\end{lstlisting}
 \end{frame}
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
diff --git a/manual/PRESENTATION_ExOth/.gitignore b/manual/PRESENTATION_ExOth/.gitignore
new file mode 100644
index 00000000..cf658897
--- /dev/null
+++ b/manual/PRESENTATION_ExOth/.gitignore
@@ -0,0 +1 @@
+*.dot
diff --git a/manual/PRESENTATION_ExOth/Makefile b/manual/PRESENTATION_ExOth/Makefile
new file mode 100644
index 00000000..a12beada
--- /dev/null
+++ b/manual/PRESENTATION_ExOth/Makefile
@@ -0,0 +1,8 @@
+
+all: scrambler_p01.pdf scrambler_p02.pdf
+
+scrambler_p01.pdf: scrambler.ys scrambler.v
+	../../yosys scrambler.ys
+
+scrambler_p02.pdf: scrambler_p01.pdf
+
diff --git a/manual/PRESENTATION_ExOth/scrambler.v b/manual/PRESENTATION_ExOth/scrambler.v
new file mode 100644
index 00000000..d4c1fa2b
--- /dev/null
+++ b/manual/PRESENTATION_ExOth/scrambler.v
@@ -0,0 +1,14 @@
+module scrambler(
+        input clk, rst, in_bit,
+        output reg out_bit
+);
+    reg [31:0] xs;
+    always @(posedge clk) begin
+    	if (rst)
+	    xs = 1;
+        xs = xs ^ (xs << 13);
+        xs = xs ^ (xs >> 17);
+        xs = xs ^ (xs << 5);
+        out_bit <= in_bit ^ xs[0];
+    end
+endmodule
diff --git a/manual/PRESENTATION_ExOth/scrambler.ys b/manual/PRESENTATION_ExOth/scrambler.ys
new file mode 100644
index 00000000..2ef14c56
--- /dev/null
+++ b/manual/PRESENTATION_ExOth/scrambler.ys
@@ -0,0 +1,23 @@
+
+read_verilog scrambler.v
+
+hierarchy; proc;;
+
+cd scrambler
+submod -name xorshift32 xs %c %ci %D %c %ci:+[D] %D %ci*:-$dff xs %co %ci %d
+cd ..
+
+show -prefix scrambler_p01 -format pdf -notitle scrambler
+show -prefix scrambler_p02 -format pdf -notitle xorshift32
+
+echo on
+
+cd xorshift32
+rename n2 in
+rename n1 out
+
+eval -set in 1 -show out
+eval -set in 270369 -show out
+
+sat -set out 632435482
+