Table notes at the bottom

I need a table to be displayed as below

The code for the table that I have written is :

 \documentclass{article}\usepackage{amsmath}\begin{document}\begin {table}[htbp]\label{table:3.6} \caption{Phase control word}\centering\footnotesize\renewcommand{\tabcolsep}{4pt}\begin{tabular}{|@{}*{18}{c|}@{}}\hline{} & {} & \multicolumn{16}{c}{Phase Control Word(Binary)}\\ \hlinefrequency & Phase  & Bit & Bit & Bit & Bit & Bit & Bit & Bit & Bit & Bit &      Bit & Bit & Bit 4 & Bit 3 & Bit 2 & Bit 1 & Bit 0\\{} & Control Word & 15 & 14 & 13 & 12 & 11 & 10 & 9 & 8 & 7 & 6 & 5 & 4 & 3  & 2 & 1 & 0\\\hline48000 & 16384 & 0 & 1 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0\\1000 & 341 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 1 & 0 & 1 & 0 & 1 & 0 & 1 & 0 & 1\\8000 & 2731 & 0 & 0 & 0 & 0 & 1 & 0 & 1 & 0 & 1 & 0 & 1 & 0 & 1 & 0 & 1 & 1\\14000 & 4779 & 0 & 0 & 0 & 1 & 0 & 0 & 1 & 0 & 1 & 0 & 1 & 1 & 1 & 1 & 1 & 1\\21000 & 7168 & 0 & 0 & 0 & 1 & 1 & 1 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0\\\hline\multicolumn{18}{l}{%  \begin{minipage}{6.5cm}% Note: [By University Requirement, no text should be allowed here in this landscape table/picture page. DON''T USE sidewaystable from rotating package, it cannot align landscape title to the left binding side.].%  \end{minipage}%}\\\end{tabular}\end{table}

This is how my output looks like-

I am missing the right margin in the right most column header and the 2nd line of table note is not center aligned. Please help me with this