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| -rw-r--r-- | manual/CHAPTER_CellLib.tex | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/manual/CHAPTER_CellLib.tex b/manual/CHAPTER_CellLib.tex index e22664a82..e64919182 100644 --- a/manual/CHAPTER_CellLib.tex +++ b/manual/CHAPTER_CellLib.tex @@ -119,6 +119,12 @@ than one bit from \B{S} is set the output is undefined. Cells of this type are u ``parallel cases'' (defined by using the {\tt parallel\_case} attribute or detected by an optimization). +The {\tt \$tribuf} cell is used to implement tristate logic. Cells of this type have a \B{WIDTH} +parameter and inputs \B{A} and \B{EN} and an output \B{Y}. The \B{A} input and \B{Y} output are +\B{WIDTH} bits wide, and the \B{EN} input is one bit wide. When \B{EN} is 0, the output \B{Y} +is not driven. When \B{EN} is 1, the value from \B{A} input is sent to the \B{Y} output. Therefore, +the {\tt \$tribuf} cell implements the function \lstinline[language=Verilog]; Y = EN ? A : 'bz;. + Behavioural code with cascaded {\tt if-then-else}- and {\tt case}-statements usually results in trees of multiplexer cells. Many passes (from various optimizations to FSM extraction) heavily depend on these multiplexer trees to @@ -398,9 +404,15 @@ Verilog & Cell Type \\ \hline \lstinline[language=Verilog]; Y = ~A; & {\tt \$\_NOT\_} \\ \lstinline[language=Verilog]; Y = A & B; & {\tt \$\_AND\_} \\ +\lstinline[language=Verilog]; Y = ~(A & B); & {\tt \$\_NAND\_} \\ +\lstinline[language=Verilog]; Y = A & ~B; & {\tt \$\_ANDNOT\_} \\ \lstinline[language=Verilog]; Y = A | B; & {\tt \$\_OR\_} \\ +\lstinline[language=Verilog]; Y = ~(A | B); & {\tt \$\_NOR\_} \\ +\lstinline[language=Verilog]; Y = A | ~B; & {\tt \$\_ORNOT\_} \\ \lstinline[language=Verilog]; Y = A ^ B; & {\tt \$\_XOR\_} \\ +\lstinline[language=Verilog]; Y = ~(A ^ B); & {\tt \$\_XNOR\_} \\ \lstinline[language=Verilog]; Y = S ? B : A; & {\tt \$\_MUX\_} \\ +\lstinline[language=Verilog]; Y = EN ? A : 'bz; & {\tt \$\_TBUF\_} \\ \hline \lstinline[language=Verilog]; always @(negedge C) Q <= D; & {\tt \$\_DFF\_N\_} \\ \lstinline[language=Verilog]; always @(posedge C) Q <= D; & {\tt \$\_DFF\_P\_} \\ @@ -423,9 +435,10 @@ $ClkEdge$ & $RstLvl$ & $RstVal$ & Cell Type \\ \end{table} Table~\ref{tab:CellLib_gates} lists all cell types used for gate level logic. The cell types -{\tt \$\_NOT\_}, {\tt \$\_AND\_}, {\tt \$\_OR\_}, {\tt \$\_XOR\_} and {\tt \$\_MUX\_} -are used to model combinatorial logic. The cell types {\tt \$\_DFF\_N\_} and {\tt \$\_DFF\_P\_} -represent d-type flip-flops. +{\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 \$\_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 @@ -477,7 +490,6 @@ Add information about {\tt \$\_DFFE\_??\_}, {\tt \$\_DFFSR\_???\_}, {\tt \$\_DLA \end{fixme} \begin{fixme} -Add information about {\tt \$\_NAND\_}, {\tt \$\_NOR\_}, {\tt \$\_XNOR\_}, {\tt \$\_ANDNOT\_}, {\tt \$\_ORNOT\_}, -{\tt \$\_AOI3\_}, {\tt \$\_OAI3\_}, {\tt \$\_AOI4\_}, and {\tt \$\_OAI4\_} cells. +Add information about {\tt \$\_AOI3\_}, {\tt \$\_OAI3\_}, {\tt \$\_AOI4\_}, and {\tt \$\_OAI4\_} cells. \end{fixme} |