diff options
Diffstat (limited to 'manual')
| -rw-r--r-- | manual/CHAPTER_CellLib.tex | 101 | ||||
| -rw-r--r-- | manual/CHAPTER_Overview.tex | 7 |
2 files changed, 97 insertions, 11 deletions
diff --git a/manual/CHAPTER_CellLib.tex b/manual/CHAPTER_CellLib.tex index 00a88cc82..55abd9b96 100644 --- a/manual/CHAPTER_CellLib.tex +++ b/manual/CHAPTER_CellLib.tex @@ -198,8 +198,8 @@ calculated signal and a constant zero with an {\tt \$and} gate). \subsection{Registers} -D-Type Flip-Flops are represented by {\tt \$dff} cells. These cells have a clock port \B{CLK}, -an input port \B{D} and an output port \B{Q}. The following parameters are available for \$dff +D-type flip-flops are represented by {\tt \$dff} cells. These cells have a clock port \B{CLK}, +an input port \B{D} and an output port \B{Q}. The following parameters are available for {\tt \$dff} cells: \begin{itemize} @@ -211,13 +211,23 @@ 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 asynchronous resets are represented by {\tt \$adff} cells. As the {\tt \$dff} +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: \begin{itemize} \item \B{ARST\_POLARITY} \\ -The asynchronous reset is high-active if this parameter has the value {\tt 1'b1} and low-active +The asynchronous 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{ARST\_VALUE} \\ @@ -231,8 +241,27 @@ 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 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, +and the following two parameters: + +\begin{itemize} +\item \B{SET\_POLARITY} \\ +The set input is active-high if this parameter has the value {\tt 1'b1} and active-low +if this parameter is {\tt 1'b0}. + +\item \B{CLR\_POLARITY} \\ +The reset 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} + +When both the set and reset inputs of a {\tt \$dffsr} cell are active, the reset input takes +precedence. + \begin{fixme} -Add information about {\tt \$sr} cells (set-reset flip-flops) and d-type latches. +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). \end{fixme} \subsection{Memories} @@ -451,6 +480,30 @@ $ClkEdge$ & $RstLvl$ & $RstVal$ & Cell Type \\ \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\_} \\ \end{tabular} +% FIXME: the layout of this is broken and I have no idea how to fix it +\hfil +\begin{tabular}[t]{lll} +$ClkEdge$ & $EnLvl$ & Cell Type \\ +\hline +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & {\tt \$\_DFFE\_NN\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & {\tt \$\_DFFE\_NP\_} \\ +\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 +\hfil +\begin{tabular}[t]{llll} +$ClkEdge$ & $SetLvl$ & $RstLvl$ & Cell Type \\ +\hline +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFFSR\_NNN\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFFSR\_NNP\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];0; & {\tt \$\_DFFSR\_NPN\_} \\ +\lstinline[language=Verilog];negedge; & \lstinline[language=Verilog];1; & \lstinline[language=Verilog];1; & {\tt \$\_DFFSR\_NPP\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];0; & {\tt \$\_DFFSR\_PNN\_} \\ +\lstinline[language=Verilog];posedge; & \lstinline[language=Verilog];0; & \lstinline[language=Verilog];1; & {\tt \$\_DFFSR\_PNP\_} \\ +\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} \end{table} @@ -459,11 +512,22 @@ Table~\ref{tab:CellLib_gates} lists all cell types used for gate level logic. Th {\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. + The cell types {\tt \$\_DFF\_N\_} and {\tt \$\_DFF\_P\_} represent d-type flip-flops. +The cell types {\tt \$\_DFFE\_NN\_}, {\tt \$\_DFFE\_NP\_}, {\tt \$\_DFFE\_PN\_} and {\tt \$\_DFFE\_PP\_} +implement d-type flip-flops with 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 (EN == $EnLvl$) + Q <= D; +\end{lstlisting} + The cell types {\tt \$\_DFF\_NN0\_}, {\tt \$\_DFF\_NN1\_}, {\tt \$\_DFF\_NP0\_}, {\tt \$\_DFF\_NP1\_}, {\tt \$\_DFF\_PN0\_}, {\tt \$\_DFF\_PN1\_}, {\tt \$\_DFF\_PP0\_} and {\tt \$\_DFF\_PP1\_} implement -d-type flip-flops with asynchronous resets. The values in the table for these cell types relate to the +d-type flip-flops with asynchronous 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;, and \lstinline[language=Verilog];negedge; otherwise. @@ -476,6 +540,25 @@ 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 +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; +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 + 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} @@ -507,11 +590,7 @@ Add information about {\tt \$ff} and {\tt \$\_FF\_} cells. \end{fixme} \begin{fixme} -Add information about {\tt \$dffe}, {\tt \$dffsr}, {\tt \$dlatch}, and {\tt \$dlatchsr} cells. -\end{fixme} - -\begin{fixme} -Add information about {\tt \$\_DFFE\_??\_}, {\tt \$\_DFFSR\_???\_}, {\tt \$\_DLATCH\_?\_}, and {\tt \$\_DLATCHSR\_???\_} cells. +Add information about {\tt \$\_DLATCH\_?\_}, and {\tt \$\_DLATCHSR\_???\_} cells. \end{fixme} \begin{fixme} diff --git a/manual/CHAPTER_Overview.tex b/manual/CHAPTER_Overview.tex index 3009bf2c0..be37d8d39 100644 --- a/manual/CHAPTER_Overview.tex +++ b/manual/CHAPTER_Overview.tex @@ -234,6 +234,8 @@ An RTLIL::Wire object has the following properties: \item The wire name \item A list of attributes \item A width (buses are just wires with a width > 1) +\item Bus direction (MSB to LSB or vice versa) +\item Lowest valid bit index (LSB or MSB depending on bus direction) \item If the wire is a port: port number and direction (input/output/inout) \end{itemize} @@ -246,6 +248,11 @@ This makes some aspects of RTLIL more complex but enables Yosys to be used for coarse grain synthesis where the cells of the target architecture operate on entire signal vectors instead of single bit wires. +In Verilog and VHDL, busses may have arbitrary bounds, and LSB can have either +the lowest or the highest bit index. In RTLIL, bit 0 always corresponds to LSB; +however, information from the HDL frontend is preserved so that the bus will be +correctly indexed in error messages, backend output, constraint files, etc. + An RTLIL::Cell object has the following properties: \begin{itemize} |