You must define the cell alignment of X column you have the options l,c,r for horizontal align, and p,m,b for vertical, to control the cell text separations you have \tabulinesep value; then you must define the table width to \linewidth and declare the size of each column and each alignment this case {X[mc]X[mc]X[mc]X[5m]} the column width is proportional to each number in the X column. see tabu manual, tabu is an extension of tabularx package, you must include it in your document.
RESULT:
MWE:
% arara: pdflatex: {synctex: yes, action: nonstopmode}
\documentclass[12pt,a4paper]{article}
\usepackage{tikz}
\usepackage{tabu}
\usepackage{tabularx}
\usepackage{booktabs}
\begin{document}
\pagestyle{empty}
\begin{table}[!ht]
\centering
\caption{Triggermogelijkheden van INT0.}
\tabulinesep = 5pt
\begin{tabu} to \linewidth {X[mc]X[mc]X[mc]X[5m]}
\tabucline -
ISC01 & ISC00 & & Omschrijving \\ \tabucline -
0 & 0 & \begin{tikzpicture}\draw (0,0.3) -- (0.3,0.3) -- (0.3,0);\draw [ultra thick] (0.3,0.0) -- (1.3,0);\draw (1.3,0) -- (1.3,0.3) -- (1.6,0.3);\end{tikzpicture} & Een laag niveau op de INT0-ingang genereert een interrupt. \\ \tabucline -
0 & 1 & \begin{tikzpicture}\draw (0,0.3) -- (0.3,0.3);\draw [ultra thick] (0.3,0.3) -- (0.3,0.0);\draw (0.3,0) -- (1.3,0);\draw [ultra thick] (1.3,0) -- (1.3,0.3);\draw (1.3,0.3) -- (1.6,0.3);\end{tikzpicture} & Een opgaande of neergaande flank op de INT0-ingang genereert een interrupt. \\ \tabucline -
1 & 0 & \begin{tikzpicture}\draw (0,0.3) -- (0.3,0.3);\draw [ultra thick] (0.3,0.3) -- (0.3,0.0);\draw (0.3,0) -- (1.3,0);\draw (1.3,0) -- (1.3,0.3);\draw (1.3,0.3) -- (1.6,0.3);\end{tikzpicture} & Een neergaande flank op de INT0-ingang genereert een interrupt. \\ \tabucline -
1 & 1 & \begin{tikzpicture}\draw (0,0.3) -- (0.3,0.3);\draw (0.3,0.3) -- (0.3,0.0);\draw (0.3,0) -- (1.3,0);\draw [ultra thick] (1.3,0) -- (1.3,0.3);\draw (1.3,0.3) -- (1.6,0.3);\end{tikzpicture} & Een opgaande flank op de INT0-ingang genereert een interrupt. \\ \tabucline -
\end{tabu}
\end{table}
\end{document}
ADDENDUM:
If you want to improve to reuse the tikz code you could define a drawing with conditional parts using \ifnum{contdition} drawing_statements \fi, and reuse a path coordinates asingning a name using coordinate(coordinate_name), so you can use the coordinate names to asign some in conditional drawings; in your example there are 3 switching objets you can control if they apear or not using values like in \sqwave[#1][#2][#3]{} each #number controls if some apears or not, in this case apears if the #number value is 1.
RESULT:
MWE:
% arara: pdflatex: {synctex: yes, action: nonstopmode}
\documentclass[12pt,a4paper]{article}
\usepackage{tikz}
\usepackage{tabu}
\usepackage{tabularx}
\usepackage{booktabs}
\begin{document}
\pagestyle{empty}
\begin{table}[!ht]
\centering
\caption{Triggermogelijkheden van INT0.}
\tabulinesep = 5pt
\def\sqwave[#1][#2][#3]{
\begin{tikzpicture}[shorten >=-0.25pt, shorten <=-0.25pt]
\draw[black!30]
(0,0.3)
-- ++ (0.3,0) coordinate (a)
-- ++ (0,-0.3) coordinate (b)
-- ++ (1,0) coordinate (c)
-- ++ (0,0.3) coordinate (d)
-- ++ (0.3,0);
\ifnum#1=1 \draw[line width=1.5pt] (a)--(b);\fi
\ifnum#2=1 \draw[line width=1.5pt] (b)--(c);\fi
\ifnum#3=1 \draw[line width=1.5pt] (c)--(d);\fi
\end{tikzpicture}
}
\begin{tabu} to \linewidth {X[mc]X[mc]X[mc]X[5m]}
\tabucline -
ISC01 & ISC00 & & Omschrijving \\ \tabucline -
0 & 0 & \sqwave[0][1][0] & Een laag niveau op de INT0-ingang genereert een interrupt. \\ \tabucline -
0 & 1 & \sqwave[1][0][1] & Een opgaande of neergaande flank op de INT0-ingang genereert een interrupt. \\ \tabucline -
1 & 0 & \sqwave[1][0][0] & Een neergaande flank op de INT0-ingang genereert een interrupt. \\ \tabucline -
1 & 1 & \sqwave[0][0][1] & Een opgaande flank op de INT0-ingang genereert een interrupt. \\ \tabucline -
\end{tabu}
\end{table}
\end{document}
\vcenterand\centering