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Diffstat (limited to 'manual/CHAPTER_CellLib.tex')
| -rw-r--r-- | manual/CHAPTER_CellLib.tex | 206 |
1 files changed, 178 insertions, 28 deletions
diff --git a/manual/CHAPTER_CellLib.tex b/manual/CHAPTER_CellLib.tex index 32c530582..25adcda86 100644 --- a/manual/CHAPTER_CellLib.tex +++ b/manual/CHAPTER_CellLib.tex @@ -234,16 +234,6 @@ Clock is active on the positive edge if this parameter has the value {\tt 1'b1} edge if this parameter is {\tt 1'b0}. \end{itemize} -D-type flip-flops with enable are represented by {\tt \$dffe} cells. As the {\tt \$dff} -cells they have \B{CLK}, \B{D} and \B{Q} ports. In addition they also have a single-bit \B{EN} -input port for the enable pin and the following parameter: - -\begin{itemize} -\item \B{EN\_POLARITY} \\ -The enable input is active-high if this parameter has the value {\tt 1'b1} and active-low -if this parameter is {\tt 1'b0}. -\end{itemize} - D-type flip-flops with asynchronous reset are represented by {\tt \$adff} cells. As the {\tt \$dff} cells they have \B{CLK}, \B{D} and \B{Q} ports. In addition they also have a single-bit \B{ARST} input port for the reset pin and the following additional two parameters: @@ -257,13 +247,26 @@ if this parameter is {\tt 1'b0}. The state of \B{Q} will be set to this value when the reset is active. \end{itemize} -Note that the {\tt \$adff} cell can only be used when the reset value is constant. - \begin{sloppypar} Usually these cells are generated by the {\tt proc} pass using the information in the designs RTLIL::Process objects. \end{sloppypar} +D-type flip-flops with synchronous reset are represented by {\tt \$sdff} cells. As the {\tt \$dff} +cells they have \B{CLK}, \B{D} and \B{Q} ports. In addition they also have a single-bit \B{SRST} +input port for the reset pin and the following additional two parameters: + +\begin{itemize} +\item \B{SRST\_POLARITY} \\ +The synchronous reset is active-high if this parameter has the value {\tt 1'b1} and active-low +if this parameter is {\tt 1'b0}. + +\item \B{SRST\_VALUE} \\ +The state of \B{Q} will be set to this value when the reset is active. +\end{itemize} + +Note that the {\tt \$adff} and {\tt \$sdff} cells can only be used when the reset value is constant. + D-type flip-flops with asynchronous set and reset are represented by {\tt \$dffsr} cells. As the {\tt \$dff} cells they have \B{CLK}, \B{D} and \B{Q} ports. In addition they also have a single-bit \B{SET} input port for the set pin, a single-bit \B{CLR} input port for the reset pin, @@ -282,9 +285,21 @@ if this parameter is {\tt 1'b0}. When both the set and reset inputs of a {\tt \$dffsr} cell are active, the reset input takes precedence. +D-type flip-flops with enable are represented by {\tt \$dffe}, {\tt \$adffe}, {\tt \$dffsre}, +{\tt \$sdffe}, and {\tt \$sdffce} cells, which are enhanced variants of {\tt \$dff}, {\tt \$adff}, {\tt \$dffsr}, +{\tt \$sdff} (with reset over enable) and {\tt \$sdff} (with enable over reset) +cells, respectively. They have the same ports and parameters as their base cell. +In addition they also have a single-bit \B{EN} input port for the enable pin and the following parameter: + +\begin{itemize} +\item \B{EN\_POLARITY} \\ +The enable input is active-high if this parameter has the value {\tt 1'b1} and active-low +if this parameter is {\tt 1'b0}. +\end{itemize} + \begin{fixme} Add information about {\tt \$sr} cells (set-reset flip-flops), {\tt \$dlatch} cells (d-type latches), -and {\tt \$dlatchsr} cells (d-type latches with set/reset). +{\tt \$adlatch} and {\tt \$dlatchsr} cells (d-type latches with set/reset). \end{fixme} \subsection{Memories} @@ -490,20 +505,29 @@ Verilog & Cell Type \\ \lstinline[language=Verilog]; always @(negedge C) Q <= D; & {\tt \$\_DFF\_N\_} \\ \lstinline[language=Verilog]; always @(posedge C) Q <= D; & {\tt \$\_DFF\_P\_} \\ \end{tabular} +\caption{Cell types for gate level logic networks (main list)} +\label{tab:CellLib_gates} +\end{table} + +\begin{table}[t] \hfil \begin{tabular}[t]{llll} $ClkEdge$ & $RstLvl$ & $RstVal$ & Cell Type \\ \hline -\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFF\_NN0\_} \\ -\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFF\_NN1\_} \\ -\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFF\_NP0\_} \\ -\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFF\_NP1\_} \\ -\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFF\_PN0\_} \\ -\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFF\_PN1\_} \\ -\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFF\_PP0\_} \\ -\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFF\_PP1\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFF\_NN0\_}, {\tt \$\_SDFF\_NN0\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFF\_NN1\_}, {\tt \$\_SDFF\_NN1\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFF\_NP0\_}, {\tt \$\_SDFF\_NP0\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFF\_NP1\_}, {\tt \$\_SDFF\_NP1\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFF\_PN0\_}, {\tt \$\_SDFF\_PN0\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFF\_PN1\_}, {\tt \$\_SDFF\_PN1\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFF\_PP0\_}, {\tt \$\_SDFF\_PP0\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFF\_PP1\_}, {\tt \$\_SDFF\_PP1\_} \\ \end{tabular} -% FIXME: the layout of this is broken and I have no idea how to fix it +\caption{Cell types for gate level logic networks (FFs with reset)} +\label{tab:CellLib_gates_adff} +\end{table} + +\begin{table}[t] \hfil \begin{tabular}[t]{lll} $ClkEdge$ & $EnLvl$ & Cell Type \\ @@ -513,7 +537,36 @@ $ClkEdge$ & $EnLvl$ & Cell Type \\ \lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & {\tt \$\_DFFE\_PN\_} \\ \lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & {\tt \$\_DFFE\_PP\_} \\ \end{tabular} -% FIXME: the layout of this is broken too +\caption{Cell types for gate level logic networks (FFs with enable)} +\label{tab:CellLib_gates_dffe} +\end{table} + +\begin{table}[t] +\begin{tabular}[t]{lllll} +$ClkEdge$ & $RstLvl$ & $RstVal$ & $EnLvl$ & Cell Type \\ +\hline +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFFE\_NN0N\_}, {\tt \$\_SDFFE\_NN0N\_}, {\tt \$\_SDFFCE\_NN0N\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFFE\_NN0P\_}, {\tt \$\_SDFFE\_NN0P\_}, {\tt \$\_SDFFCE\_NN0P\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFFE\_NN1N\_}, {\tt \$\_SDFFE\_NN1N\_}, {\tt \$\_SDFFCE\_NN1N\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFFE\_NN1P\_}, {\tt \$\_SDFFE\_NN1P\_}, {\tt \$\_SDFFCE\_NN1P\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFFE\_NP0N\_}, {\tt \$\_SDFFE\_NP0N\_}, {\tt \$\_SDFFCE\_NP0N\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFFE\_NP0P\_}, {\tt \$\_SDFFE\_NP0P\_}, {\tt \$\_SDFFCE\_NP0P\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFFE\_NP1N\_}, {\tt \$\_SDFFE\_NP1N\_}, {\tt \$\_SDFFCE\_NP1N\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFFE\_NP1P\_}, {\tt \$\_SDFFE\_NP1P\_}, {\tt \$\_SDFFCE\_NP1P\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFFE\_PN0N\_}, {\tt \$\_SDFFE\_PN0N\_}, {\tt \$\_SDFFCE\_PN0N\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFFE\_PN0P\_}, {\tt \$\_SDFFE\_PN0P\_}, {\tt \$\_SDFFCE\_PN0P\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFFE\_PN1N\_}, {\tt \$\_SDFFE\_PN1N\_}, {\tt \$\_SDFFCE\_PN1N\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFFE\_PN1P\_}, {\tt \$\_SDFFE\_PN1P\_}, {\tt \$\_SDFFCE\_PN1P\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFFE\_PP0N\_}, {\tt \$\_SDFFE\_PP0N\_}, {\tt \$\_SDFFCE\_PP0N\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFFE\_PP0P\_}, {\tt \$\_SDFFE\_PP0P\_}, {\tt \$\_SDFFCE\_PP0P\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFFE\_PP1N\_}, {\tt \$\_SDFFE\_PP1N\_}, {\tt \$\_SDFFCE\_PP1N\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFFE\_PP1P\_}, {\tt \$\_SDFFE\_PP1P\_}, {\tt \$\_SDFFCE\_PP1P\_} \\ +\end{tabular} +\caption{Cell types for gate level logic networks (FFs with reset and enable)} +\label{tab:CellLib_gates_adffe} +\end{table} + +\begin{table}[t] \hfil \begin{tabular}[t]{llll} $ClkEdge$ & $SetLvl$ & $RstLvl$ & Cell Type \\ @@ -527,11 +580,37 @@ $ClkEdge$ & $SetLvl$ & $RstLvl$ & Cell Type \\ \lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFFSR\_PPN\_} \\ \lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFFSR\_PPP\_} \\ \end{tabular} -\caption{Cell types for gate level logic networks} -\label{tab:CellLib_gates} +\caption{Cell types for gate level logic networks (FFs with set and reset)} +\label{tab:CellLib_gates_dffsr} +\end{table} + +\begin{table}[t] +\hfil +\begin{tabular}[t]{lllll} +$ClkEdge$ & $SetLvl$ & $RstLvl$ & $EnLvl$ & Cell Type \\ +\hline +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFFSRE\_NNNN\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFFSRE\_NNNP\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFFSRE\_NNPN\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFFSRE\_NNPP\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFFSRE\_NPNN\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFFSRE\_NPNP\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFFSRE\_NPPN\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFFSRE\_NPPP\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFFSRE\_PNNN\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFFSRE\_PNNP\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFFSRE\_PNPN\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFFSRE\_PNPP\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFFSRE\_PPNN\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFFSRE\_PPNP\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFFSRE\_PPPN\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFFSRE\_PPPP\_} \\ +\end{tabular} +\caption{Cell types for gate level logic networks (FFs with set and reset and enable)} +\label{tab:CellLib_gates_dffsre} \end{table} -Table~\ref{tab:CellLib_gates} lists all cell types used for gate level logic. The cell types +Tables~\ref{tab:CellLib_gates}, \ref{tab:CellLib_gates_dffe}, \ref{tab:CellLib_gates_adff}, \ref{tab:CellLib_gates_adffe}, \ref{tab:CellLib_gates_dffsr} and \ref{tab:CellLib_gates_dffsre} list all cell types used for gate level logic. The cell types {\tt \$\_NOT\_}, {\tt \$\_AND\_}, {\tt \$\_NAND\_}, {\tt \$\_ANDNOT\_}, {\tt \$\_OR\_}, {\tt \$\_NOR\_}, {\tt \$\_ORNOT\_}, {\tt \$\_XOR\_}, {\tt \$\_XNOR\_} and {\tt \$\_MUX\_} are used to model combinatorial logic. The cell type {\tt \$\_TBUF\_} is used to model tristate logic. @@ -563,8 +642,61 @@ otherwise. Q <= D; \end{lstlisting} -The cell types {\tt \$\_DFFSR\_NNN\_}, {\tt \$\_DFFSR\_NNP\_}, {\tt \$\_DFFSR\_NPN\_}, {\tt \$\_DFFSR\_NPP\_}, -{\tt \$\_DFFSR\_PNN\_}, {\tt \$\_DFFSR\_PNP\_}, {\tt \$\_DFFSR\_PPN\_} and {\tt \$\_DFFSR\_PPP\_} implement +The cell types {\tt \$\_SDFF\_NN0\_}, {\tt \$\_SDFF\_NN1\_}, {\tt \$\_SDFF\_NP0\_}, {\tt \$\_SDFF\_NP1\_}, +{\tt \$\_SDFF\_PN0\_}, {\tt \$\_SDFF\_PN1\_}, {\tt \$\_SDFF\_PP0\_} and {\tt \$\_SDFF\_PP1\_} implement +d-type flip-flops with synchronous reset. The values in the table for these cell types relate to the +following Verilog code template: + +\begin{lstlisting}[mathescape,language=Verilog] + always @($ClkEdge$ C) + if (R == $RstLvl$) + Q <= $RstVal$; + else + Q <= D; +\end{lstlisting} + +The cell types {\tt \$\_DFFE\_[NP][NP][01][NP]\_} implement +d-type flip-flops with asynchronous reset and enable. The values in the table for these cell types relate to the +following Verilog code template, where \lstinline[mathescape,language=Verilog];$RstEdge$; is \lstinline[language=Verilog];posedge; +if \lstinline[mathescape,language=Verilog];$RstLvl$; if \lstinline[language=Verilog];1;, and \lstinline[language=Verilog];negedge; +otherwise. + +\begin{lstlisting}[mathescape,language=Verilog] + always @($ClkEdge$ C, $RstEdge$ R) + if (R == $RstLvl$) + Q <= $RstVal$; + else if (EN == $EnLvl$) + Q <= D; +\end{lstlisting} + +The cell types {\tt \$\_SDFFE\_[NP][NP][01][NP]\_} implement d-type flip-flops +with synchronous reset and enable, with reset having priority over enable. +The values in the table for these cell types relate to the +following Verilog code template: + +\begin{lstlisting}[mathescape,language=Verilog] + always @($ClkEdge$ C) + if (R == $RstLvl$) + Q <= $RstVal$; + else if (EN == $EnLvl$) + Q <= D; +\end{lstlisting} + +The cell types {\tt \$\_SDFFCE\_[NP][NP][01][NP]\_} implement d-type flip-flops +with synchronous reset and enable, with enable having priority over reset. +The values in the table for these cell types relate to the +following Verilog code template: + +\begin{lstlisting}[mathescape,language=Verilog] + always @($ClkEdge$ C) + if (EN == $EnLvl$) + if (R == $RstLvl$) + Q <= $RstVal$; + else + Q <= D; +\end{lstlisting} + +The cell types {\tt \$\_DFFSR\_[NP][NP][NP]\_} implement d-type flip-flops with asynchronous set and reset. The values in the table for these cell types relate to the following Verilog code template, where \lstinline[mathescape,language=Verilog];$RstEdge$; is \lstinline[language=Verilog];posedge; if \lstinline[mathescape,language=Verilog];$RstLvl$; if \lstinline[language=Verilog];1;, \lstinline[language=Verilog];negedge; @@ -582,6 +714,24 @@ otherwise. Q <= D; \end{lstlisting} +The cell types {\tt \$\_DFFSRE\_[NP][NP][NP][NP]\_} implement +d-type flip-flops with asynchronous set and reset and enable. The values in the table for these cell types relate to the +following Verilog code template, where \lstinline[mathescape,language=Verilog];$RstEdge$; is \lstinline[language=Verilog];posedge; +if \lstinline[mathescape,language=Verilog];$RstLvl$; if \lstinline[language=Verilog];1;, \lstinline[language=Verilog];negedge; +otherwise, and \lstinline[mathescape,language=Verilog];$SetEdge$; is \lstinline[language=Verilog];posedge; +if \lstinline[mathescape,language=Verilog];$SetLvl$; if \lstinline[language=Verilog];1;, \lstinline[language=Verilog];negedge; +otherwise. + +\begin{lstlisting}[mathescape,language=Verilog] + always @($ClkEdge$ C, $RstEdge$ R, $SetEdge$ S) + if (R == $RstLvl$) + Q <= 0; + else if (S == $SetLvl$) + Q <= 1; + else if (E == $EnLvl$) + Q <= D; +\end{lstlisting} + In most cases gate level logic networks are created from RTL networks using the {\tt techmap} pass. The flip-flop cells from the gate level logic network can be mapped to physical flip-flop cells from a Liberty file using the {\tt dfflibmap} pass. The combinatorial logic cells can be mapped to physical cells from a Liberty file via ABC \citeweblink{ABC} |