From 9ab850e45eb907a6778c62eace974221d18b49c2 Mon Sep 17 00:00:00 2001 From: Clifford Wolf Date: Sat, 23 Nov 2013 05:46:51 +0100 Subject: [PATCH] Making prograss on Appnote 010 --- manual/APPNOTE_010_Verilog_to_BLIF.tex | 100 +++++++++++++++++++++++-- manual/appnote.tex | 1 + 2 files changed, 93 insertions(+), 8 deletions(-) diff --git a/manual/APPNOTE_010_Verilog_to_BLIF.tex b/manual/APPNOTE_010_Verilog_to_BLIF.tex index 30e9839f4..514f50e2d 100644 --- a/manual/APPNOTE_010_Verilog_to_BLIF.tex +++ b/manual/APPNOTE_010_Verilog_to_BLIF.tex @@ -50,10 +50,14 @@ the BLIF format, for example it only uses synchronous resets. Converting {\tt softusb\_navre.v} to {\tt softusb\_navre.blif} could not be easier: +\begin{figure}[H] \begin{lstlisting}[frame=trBL,xleftmargin=1.5em,numbers=left] - yosys -o softusb_navre.blif \ - -S softusb_navre.v +yosys -o softusb_navre.blif \ + -S softusb_navre.v \end{lstlisting} + \renewcommand{\figurename}{Listing} +\caption{Calling Yosys without script file} +\end{figure} Behind the scenes Yosys is controlled by synthesis scripts that execute commands that operate on Yosys' internal state. For example, the {\tt -o @@ -76,12 +80,16 @@ to use an actual script file. With a script file we have better control over Yosys. The following script file replicates what the command from the last section did: -\begin{lstlisting}[frame=trBL,xleftmargin=1.5em,numbers=left,caption={\tt softusb\_navre.ys}] +\begin{figure}[H] +\begin{lstlisting}[frame=trBL,xleftmargin=1.5em,numbers=left] read_verilog softusb_navre.v hierarchy proc; opt; memory; opt; techmap; opt write_blif softusb_navre.blif \end{lstlisting} + \renewcommand{\figurename}{Listing} +\caption{\tt softusb\_navre.ys} +\end{figure} The first and last line obviously read the Verilog file and write the BLIF file. @@ -124,9 +132,13 @@ source file, as we will see in the next section. Now Yosys can be run with the file of the synthesis script as argument: +\begin{figure}[H] \begin{lstlisting}[frame=trBL,xleftmargin=1.5em,numbers=left] - yosys softusb_navre.ys +yosys softusb_navre.ys \end{lstlisting} + \renewcommand{\figurename}{Listing} +\caption{Calling Yosys with script file} +\end{figure} \medskip @@ -155,13 +167,17 @@ processed using custom commands. But in this case we don't need that. So now we have the final synthesis script for generating a BLIF file for the navre CPU: -\begin{lstlisting}[frame=trBL,xleftmargin=1.5em,numbers=left,caption={\tt softusb\_navre.ys} (improved)] +\begin{figure}[H] +\begin{lstlisting}[frame=trBL,xleftmargin=1.5em,numbers=left] read_verilog softusb_navre.v hierarchy -check -top softusb_navre proc; opt; memory; opt; fsm; opt; techmap; opt write_blif softusb_navre.blif \end{lstlisting} + \renewcommand{\figurename}{Listing} +\caption{{\tt softusb\_navre.ys} (improved)} +\end{figure} \section{Advanced Example: The Amber23 ARMv2a CPU} @@ -169,7 +185,8 @@ Our 2nd example is the Amber23\footnote{\url{http://opencores.org/project,amber} ARMv2a CPU. Once again we base our example on the Verilog code that is included in {\it yosys-bigsim}. -\begin{lstlisting}[frame=trBL,xleftmargin=1.5em,numbers=left,caption={\tt amber23.ys}] +\begin{figure}[b!] +\begin{lstlisting}[frame=trBL,xleftmargin=1.5em,numbers=left] read_verilog a23_alu.v read_verilog a23_barrel_shift_fpga.v read_verilog a23_barrel_shift.v @@ -188,10 +205,77 @@ read_verilog generic_sram_line_en.v hierarchy -check -top a23_core add -global_input globrst 1 proc -global_arst globrst -opt; memory; opt; fsm; opt techmap -map adff2dff.v -techmap +opt; memory; opt; fsm; opt; techmap write_blif amber23.blif \end{lstlisting} + \renewcommand{\figurename}{Listing} +\caption{\tt amber23.ys} +\label{aber23.ys} +\end{figure} + +The problem with this core is that it contains no dedicated reset signals. +Instead it is using the coding techiques shown in Listing~\ref{glob_arst} to +set reset values to be used on the global asynchronous reset in an FPGA +implementation. This design can not be expressed in BLIF as it is. Instead we +need to use a synthesis script that transforms this to synchonous resets that +can be expressed in BLIF. + +\medskip + +Listing~\ref{aber23.ys} shows the synthesis script for the Amber23 core. In +line 17 the {\tt add} command is used to add a 1-bit wide global input signal +with the name {\tt globrst}. That means that an input with that name is added +to each module in the design hierarchy and then all module instanciations are +altered so that this new signal is connected throughout the whole design +hierarchy. + +\begin{figure}[t!] +\begin{lstlisting}[frame=trBL,xleftmargin=1.5em,numbers=left] +reg [7:0] a = 13, b; +initial b = 37; +\end{lstlisting} + \renewcommand{\figurename}{Listing} +\caption{Implicit coding of global asynchronous resets} +\label{glob_arst} +\end{figure} + +\begin{figure}[b!] +\begin{lstlisting}[frame=trBL,xleftmargin=1.5em,numbers=left] +module \$adff (CLK, ARST, D, Q); + +parameter WIDTH = 1; +parameter CLK_POLARITY = 1'b1; +parameter ARST_POLARITY = 1'b1; +parameter ARST_VALUE = 0; + +input CLK, ARST; +input [WIDTH-1:0] D; +output reg [WIDTH-1:0] Q; + +wire _TECHMAP_FAIL_ = + !CLK_POLARITY || !ARST_POLARITY; + +always @(posedge CLK) + if (ARST) + Q <= ARST_VALUE; + else + Q <= D; + +endmodule +\end{lstlisting} + \renewcommand{\figurename}{Listing} +\caption{\tt adff2dff.v} +\label{adff2dff.v} +\end{figure} + +In line 18 the {\tt proc} command is called. But this time the newly created +reset signal is passed to the core as a global reset line to use for resetting +all registers to their initial values. + +Finally in line 19 the {\tt techmap} command is used to replace all instances +of flip-flops with asynchronous resets to flip-flops with synchronous resets. +The map file used fo this is shown in Lising~\ref{adff2dff.v}. +{\color{red} FIXME} diff --git a/manual/appnote.tex b/manual/appnote.tex index f8b14e42f..4c543d6ae 100644 --- a/manual/appnote.tex +++ b/manual/appnote.tex @@ -22,6 +22,7 @@ \usepackage{multirow} \usepackage{hhline} \usepackage{listings} +\usepackage{float} \usepackage{tikz} \usetikzlibrary{calc} -- 2.30.2