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\documentclass[border=2mm]{standalone}
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\usepackage{tikz,fontspec}
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\usetikzlibrary{chains, scopes, patterns,
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                decorations.pathreplacing}
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% Font used for hex numbers
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% https://tug.org/FontCatalogue/typewriterfonts.html
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\newfontfamily\HexFont{Noto Sans Mono}
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% register number depend color
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\tikzset{%
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    register color/.code={%
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    \pgfmathparse{%
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        ifthenelse(#1<=7, "blue!10",%
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        ifthenelse(#1<=12,"blue!20",%
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        ifthenelse(#1==13,"yellow!30",%
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        ifthenelse(#1==14,"green!10",%
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        "green!20"%
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        )%
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        )%
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        )%
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        )%
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    }\colorlet{RegColor}{\pgfmathresult}%
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    },
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    % special
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    sregister color/.code={%
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    \pgfmathparse{%
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        ifthenelse(#1==0,"green!70",%
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        ifthenelse(or(#1>=1, #1<=3),"red!10",%
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        "red!60"%
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        )%
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        )%
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    }\colorlet{SRegColor}{\pgfmathresult}%
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    },
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}
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\begin{document}
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\begin{tikzpicture}[
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    start chain = D going below,            % register Data - chain 'D'
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    node distance = 0mm and 20mm,
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    font=\sffamily,
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    N/.style = {draw,                       % style for drawing nodes
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                minimum height={height("0xAA BB CC DD")+2pt},
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                minimum width={width("0xAA BB CC DD")+2pt},
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                outer sep=0pt, text opacity=1, align=center,
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    },
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    N/.default = red!70,
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  ]
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  %% data
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  \begin{scope}[nodes=on chain=D]
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    \tikzset{
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        every node/.append style={
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            draw,
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            font=\HexFont,
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            register color=#1, fill=RegColor
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        }
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    }
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    \foreach \r in {0, 1,...,15}{           % register data
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        \ifnum\r<7
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            \node[on chain=D, register color={\r}] {0xAA BB CC DD};
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        \else
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            \ifnum\r=9
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                \node[on chain=D, register color={\r}, text=blue] {0xAA FF FF EE};
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            \else
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                \node[on chain=D, register color={\r}] {0x00 11 22 33};
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            \fi
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        \fi
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    }
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  \end{scope}
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  % endian
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  \node[above] at (D-1.north west) {MSB};
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  \node[above] at (D-1.north east) {LSB};
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  % mapping
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  \node (A) [N, register color=13, fill=RegColor, fill opacity=0.5, above right=2mm and 8mm of D-14.east]{case A};
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  \node (B) [N, register color=13, fill=RegColor, fill opacity=0.8, right=5mm of D-14]{case B};
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  \draw[densely dashed]   (D-14.north east) -- (A.north west)
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                          (D-14.south east) -- (B.south west);  
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  %% special
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  \begin{scope}[
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      nodes=on chain, 
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      start chain = S going below
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    ]
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    \tikzset{
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        every node/.append style={
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            draw,
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            font=\HexFont,
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            sregister color=#1, fill=SRegColor
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        }
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    }    
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    \node[N, sregister color=0, fill=SRegColor, , below=5mm of D-16] {0x00 00 00 FF};
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    \node[N, sregister color=1, fill=SRegColor, ] {0x11 11 11 00};
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    \node[N, sregister color=2, fill=SRegColor, ] {0x22 22 22 00};
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    \node[N, sregister color=3, fill=SRegColor, ] {0x33 33 33 00};
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    \node[N, sregister color=4, fill=SRegColor, ] {0x44 44 44 00}; %% TBD: not red!60
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  \end{scope}
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\end{tikzpicture}
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\end{document}
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