\documentclass[a4paper]{article}

\usepackage{pgfplots}


\begin{document}

\begin{tikzpicture}
%\tracingcommands=2\tracingmacros=2
	\begin{axis}[minor ytick=data]
	\addplot {x^2};	
	\end{axis}
\end{tikzpicture}

\begin{tikzpicture}
%\tracingcommands=2\tracingmacros=2
	\begin{axis}[minor xtick=data]
	\addplot {x^2};	
	\end{axis}
\end{tikzpicture}
\end{document}

