%%This is a very basic article template.
%%There is just one section and two subsections.
\documentclass[a4paper,11pt]{article}
\usepackage{graphicx}
\usepackage[colorlinks= true]{hyperref}
\usepackage{color}
\usepackage{tabularx}

\begin{document}

   \hypersetup{
     pdfborder    = 0 0 0 1,
     colorlinks   =  true,
     linkcolor    =  black,
     urlcolor     =  blue,
     pdftitle     = {Issues in EDA-02446-V1-0},
     pdfauthor    = {Carlos Gil Soriano},
     pdfsubject   = {Issues report in EDA-02446-V1-0},
     pdfkeywords  = {Blocking, EDA-02446, CONV-TTL-BLO}
   }


   \title{\textbf{Report of issues in CONV-TTL-BLO v1.0\\
   EDA-02446-V1-0}}
   \author{Carlos Gil Soriano\\BE-CO-HT\\
   \href{mailto:carlos.gil.soriano@cern.ch}{
                      \textbf{\textit{carlos.gil.soriano@cern.ch}}}}
   \date{October 2, 2012}
   \maketitle
   \thispagestyle{empty}
   \begin{figure}[htb]
      \begin{center}
         \includegraphics[scale=0.25,
         keepaspectratio]{../../../../doc/OHWR/Pictures/Figures/CERN-Logo.png}
      \end{center}
   \end{figure}

\begin{abstract}

CONV-TTL-BLO V1-0, internally named as
\href{https://edms.cern.ch/nav/P:EDA-02446:V0/I:EDA-02446-V1-0:V0/TAB4}{\textbf{EDA-02446-V1-0}}, has several \textbf{bugs to be
fixed in V2}. The present report covers them all.

\end{abstract}

  \vspace{2cm}
  \begin{center}
  \begin{tabular}{|p{2.5cm}|p{3.5cm}|p{3cm}|}
  \hline
  \multicolumn{3}{|c|}{\textbf{Revision history}}\\
     \hline
     \hline
     \textbf{HDL version} & \textbf{Module} & \textbf{Date}\\
        \hline
        1.0 & Initial report & October 2, 2012\\
           \hline
  \end{tabular}
  \end{center}

\pagebreak
\tableofcontents
\pagebreak
\listoftables
\pagebreak

\section{Power supply 24 volts}

Some resistors and capacitors should be changed to achieved better stability in
the 24 volts power supply rail.\\

\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issues 452, 455, 458 } & \url{http://www.ohwr.org/issues/458}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
         \begin{minipage}[t]{0.95\columnwidth}%
         After carefully checking the design (against the calculations provided by
         TI in its datasheet and SwitcherPro Desktop for checking the gain and phase
         margin) some modifications are submitted for an improved control of the 24V
         rail.
                  \vspace{0.125cm}
         \end{minipage}}\\
      \hline
      \multicolumn{2}{|l|}{
         \begin{minipage}[t]{0.95\columnwidth}%
 
                  \vspace{0.125cm}

         \textbf{DESIGN VALUES}
           \begin{itemize}
           \item Switching Frecuency: 475Khz
           \item Crossover Frecuency: 23.75KHz
           \item Vin : 12V
           \item Vout : 24V
           \item Feedback network: R$_{high}$  50K, R$_{low}$  1K51
           \item Compensation network: R$_{comp}$  13K35, C$_{comp}$
           4.7$\mu$F, C$_{pole}$  68$\mu$F (upto 100$\mu$F)
           \item RC network: R$_{RC}$  335K, C$_{RC}$  100pF
           \end{itemize}
                  \vspace{0.0625cm}
         \end{minipage}}\\
      \hline
    \end{tabularx}
    \caption{Issue 458: 24 volts power supply}
  \end{center}
\end{table}

\textbf{CHANGES OF COMPONENTS}\\

\begin{center}
    \begin{tabular}{|c|c|}
    \hline
    \multicolumn{2}{|c|}{\textbf{R$_{high}$}}\\
    \hline
    \hline
    \textbf{Resistor} & \textbf{Value} \\ 
    \hline
    R231 &  not changed (10K)  \\
    \hline
    R232 &  not changed (10K)  \\
    \hline
    R233 &  not changed (10K)  \\
    \hline
    R235 &  not changed (10K)  \\
    \hline
    R234 &  4K7 changed to 10K \\
    \hline
    \end{tabular}

       \vspace{0.5cm}

    \begin{tabular}{|c|c|}
    \hline
    \multicolumn{2}{|c|}{\textbf{R$_{low}$}}\\
    \hline
    \hline
    \textbf{Resistor} & \textbf{Value} \\ 
    \hline
    R229 &  100 changed to 510R \\ 
    \hline
    R230 &  4K7 changed to 1K   \\ 
    \hline
    \end{tabular}

       \vspace{0.5cm}

    \begin{tabular}{|c|c|}
    \hline
    \multicolumn{2}{|c|}{\textbf{R$_{comp}$}}\\
    \hline
    \hline
    \textbf{Resistor} & \textbf{Value} \\ 
    \hline
     R254 & 10K changed to 4K7 \\
    \hline
     R255 & 10K changed to 4K7 \\
    \hline
     R256 & 10K changed to 1K  \\
    \hline
     R257 & 10K changed to 100R\\
    \hline
     R258 & not changed (10K)  \\
    \hline
    \end{tabular}

       \vspace{0.5cm}

    \begin{tabular}{|c|c|}
    \hline
    \multicolumn{2}{|c|}{\textbf{C$_{comp}$}}\\
    \hline
    \hline
    \textbf{Capacitor} & \textbf{Value} \\ 
    \hline
     C45  & not changed (4.7 $\mu$F)\\
    \hline
    \end{tabular}

       \vspace{0.5cm}

    \begin{tabular}{|c|c|}
    \hline
    \multicolumn{2}{|c|}{\textbf{C$_{pole}$}}\\
    \hline
    \hline
    \textbf{Capacitor} & \textbf{Value} \\ 
    \hline
     C190 & 100pF removed\\
    \hline
     C191 & 100pF changed to  68pF\\
          & (100pF can be used, as well)\\
    \hline
    \end{tabular}

       \vspace{0.5cm}

    \begin{tabular}{|c|c|}
    \hline
    \multicolumn{2}{|c|}{\textbf{R$_{RC}$}}\\
    \hline
    \hline
    \textbf{Resistor} & \textbf{Value} \\ 
    \hline
     R261 & 470K changed to 100K\\
    \hline
     R262 & not changed (470K)\\
    \hline
     R263 & not changed (470K)\\
    \hline
    \end{tabular}

       \vspace{0.5cm}

    \begin{tabular}{|c|c|}
    \hline
    \multicolumn{2}{|c|}{\textbf{C$_{RC}$}}\\
    \hline
    \hline
    \textbf{Capacitor} & \textbf{Value} \\ 
    \hline
     C196 & not changed (100pF)\\
    \hline
    \end{tabular}

       \vspace{0.5cm}

    \begin{tabular}{|c|c|}
    \hline
    \multicolumn{2}{|c|}{\textbf{R$_{isns}$}}\\
    \hline
    \hline
    \textbf{Resistor} & \textbf{Value} \\ 
    \hline
     R259 & 100R changed to 1K\\
    \hline
    \end{tabular}

       \vspace{0.5cm}

    \begin{tabular}{|c|c|}
    \hline
    \multicolumn{2}{|c|}{\textbf{Output ceramic capacitors}}\\
    \hline
    \hline
    \textbf{Capacitor} & \textbf{Value} \\ 
    \hline
     C192 & Not mounted \\
    \hline
     C193 & Not mounted \\
    \hline
     C189 & Not mounted \\
    \hline
    \end{tabular}
\end{center}

\pagebreak

\section{Power line filter to be added}
\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue 517} & \url{http://www.ohwr.org/issues/517}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
         In CONV-TLL-BLO v1 no power supply filters are mounted.
         
         Due to the logic families used in the design, noise in the vicinity of
         60MHz to 150MHz was expected. Spectral measurements in the power rails
         and FFT null-magnetic tests checked the presence of this noise.
         
         Thus, a filter schema for this band is needed. The following simple
         solution consisting of a one-stage pi filter with the following values:
         \begin{itemize}
         \item Capacitor to external power rails: 22$\mu$F ceramic
         \item Capacitor to board input power rails: 150$\mu$F OSCON
         \item Inductor: Murata BLM41PG181SN1L
         \end{itemize}

         This filter stage is mounted in CONV-TTL-RS485, as well.\\
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 517: Power line filter}
  \end{center}
\end{table}

\section{Optoisolator resistor}
\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue 520} & \url{http://www.ohwr.org/issues/520}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
         Blocking input should change the value of one resistor to reduce
         degradations of diode in the optoisolator.

         Taking EDA schematics document as reference and going to page 10. R222
         resistor, which is 100R must be replaced for 1K. Thus, a maximum value
         of 22 mA is driven into the LED of the optoisolator.

         Do the same for R227,R219, R217, R215 and R226.
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 520: Optoisolator resistor}
  \end{center}
\end{table}

\textbf{CHANGES OF COMPONENTS}\\

\begin{center}
    \begin{tabular}{|c|c|}
    \hline
    \textbf{Resistor} & \textbf{Value} \\ 
    \hline
    \hline
     R215 & 100R changed to 1K \\ 
    \hline
     R217 & 100R changed to 1K \\ 
    \hline
     R219 & 100R changed to 1K \\ 
    \hline
     R222 & 100R changed to 1K \\ 
    \hline
     R226 & 100R changed to 1K \\ 
    \hline
     R227 & 100R changed to 1K \\ 
    \hline
    \end{tabular}
\end{center}


\section{Bad VME64x connections}
It represents a problem when other boards try to use the bus granted pins or
interrupt acknowledge lines.
\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue 502} & \url{http://www.ohwr.org/issues/502}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
          Some VME64 lines are misconnected.

          Daisy-chain \textit{BGxIN\_N}, \textit{BGxOUT\_N} and \textit{IACKIN\_N},
          \textit{IACKOUT\_N}.
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 502: VME64x misconnections}
  \end{center}
\end{table}

\section{Blocking driver stage}
\subsection{Misconnection of output enable pin}
\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue 463} & \url{http://www.ohwr.org/issues/463}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
         In IC3, there's a bad net name yielding into an unwanted floating pin (pin 13).

         The net name in the corresponding schematic page must be changed.
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 463: bad net name in IC3}
  \end{center}
\end{table}

\textbf{CHANGES IN SCHEMATICS}\\

\begin{center}
    \begin{tabular}{|c|c|}
    \hline
    \multicolumn{2}{|c|}{\textbf{IC3}}\\
    \hline
    \hline
    \textbf{Pin number} & \textbf{Value} \\ 
    \hline
      13 & OE\_N\_ANTIGLITCH changed to\\
         & ANTIGLITCH\_OE\_N\\
    \hline
    \end{tabular}
\end{center}

In addition, power supply must be changed. It is explained in the next section.

\pagebreak

\section{Blocking module changes}


\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue 462} & \url{http://www.ohwr.org/issues/462}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
         The blocking modules must face some profiling. The
         changes address three points:
         
         \begin{itemize}
         \item Being less temperature resistance.
         \item Improve operating point of the MOSFET (be fully conducting).
         \item Improve RC constant after pulse is outputed. 
         \end{itemize}
                  \vspace{0.125cm}
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 462: Blocking module changes}
  \end{center}
\end{table}


\subsection{Eliminate temperature issues}

Due to kT relationship, the gate diode must be removed.

\textbf{CHANGES OF COMPONENTS}\\

\begin{center}
    \begin{tabular}{|c|c|}
    \hline
    \textbf{Diode} & \textbf{Value} \\ 
    \hline
    \hline
     D69 & Remove \\
    \hline
     D45 & Remove \\
    \hline
     D21 & Remove \\
    \hline
     D65 & Remove \\
    \hline
     D41 & Remove \\
    \hline
     D17 & Remove \\
    \hline
     D61 & Remove \\
    \hline
     D37 & Remove \\
    \hline
     D13 & Remove \\
    \hline
     D67 & Remove \\
    \hline
     D43 & Remove \\
    \hline
     D19 & Remove \\
    \hline
     D63 & Remove \\
    \hline
     D39 & Remove \\
    \hline
     D15 & Remove \\
    \hline
     D59 & Remove \\
    \hline
     D35 & Remove \\
    \hline
     D11 & Remove \\
    \hline
    \end{tabular}
\end{center}


\subsection{Increase power supply of driver stage}

Driver stage must be powered at recommended 5 volts. It permits MOSFETs to be
fully conducting.

The change affects to all BCT25244 (IC2 and IC3).\\

\textbf{CHANGES OF CONNECTIONS}\\

\begin{center}
    \begin{tabular}{|c|c|}
    \hline
    \multicolumn{2}{|c|}{\textbf{BCT25244}}\\
    \hline
    \hline
    \textbf{IC} & \textbf{Value} \\ 
    \hline
    IC1 &   Power pin to 5V\\
    \hline
    IC2 &   Power pin to 5V\\
    \hline
    IC3 &   Power pin to 5V\\
    \hline
    \end{tabular}
\end{center}

\subsection{Output resistors: change and add}

To better balancing the deal between fast draining and steady on-current, the
100R output resistors must be changed to 1K.\\

\textbf{CHANGES OF COMPONENTS}\\

\begin{center}
    \begin{tabular}{|c|c|}
    \hline
    \textbf{Resistor} & \textbf{Value} \\ 
    \hline
    \hline
     R196 & 100R change to 1K\\
    \hline
     R152 & 100R change to 1K\\
    \hline
     R118 & 100R change to 1K\\
    \hline
     R192 & 100R change to 1K\\
    \hline
     R148 & 100R change to 1K\\
    \hline
     R114 & 100R change to 1K\\
    \hline
     R188 & 100R change to 1K\\
    \hline
     R144 & 100R change to 1K\\
    \hline
     R110 & 100R change to 1K\\
    \hline
     R194 & 100R change to 1K\\
    \hline
     R150 & 100R change to 1K\\
    \hline
     R116 & 100R change to 1K\\
    \hline
     R190 & 100R change to 1K\\
    \hline
     R146 & 100R change to 1K\\
    \hline
     R112 & 100R change to 1K\\
    \hline
     R186 & 100R change to 1K\\
    \hline
     R142 & 100R change to 1K\\
    \hline
     R108 & 100R change to 1K\\
    \hline
    \end{tabular}
\end{center}

In addition, an external 1K after the protection diode must be added to
place a small load at the output when no external load is connected.

\textbf{CHANGES OF COMPONENTS}\\

\begin{center}
    \begin{tabular}{|c|c|}
    \hline
    \textbf{Resistor} & \textbf{Value} \\ 
    \hline
    \hline
    R[x] &  Add 1K after the output protection diode  \\
    \hline
    \end{tabular}
\end{center}


\section{Square LED array}
\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue 570} & \url{http://www.ohwr.org/issues/570}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
         The front panel three LED array will be changed by a Dialight 568 model.
         
         This model is a bicolour (red-green) 4-LEDs array, which will be
         driven by a VME buffer to reduce BOM.

         Already done in CONV-TTL-RS485.\\
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 570: square LED array}
  \end{center}
\end{table}



\pagebreak
\section{Other issues}

\subsection{Change of logic family for Schmitt triggers}

As done in CONV-TTL-RS485, ACT family is changed for LVT family for all the
Schmitt triggers.

\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue 603} & \url{http://www.ohwr.org/issues/603}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
        To allow better compatibility between different modules, LVT family
        will subsitute ACT one because of its wider use as logic level
        translator.
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 603: Change of logic family for Schmitt triggers}
  \end{center}
\end{table}



\subsection{Separate control lines for DACs}

As done in CONV-TTL-RS485, separate control of the DACs has been included.

\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue 604} & \url{http://www.ohwr.org/issues/604}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
        According to Javier's recommendation, now the control lines are
        independent for every DAC.
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 604: Separate control lines for DACs}
  \end{center}
\end{table}


\subsection{Board Test Points}

\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue  449} & \url{http://www.ohwr.org/issues/449}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
        Test points should not be mounted in production boards.
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 449: Test points}
  \end{center}
\end{table}

\pagebreak

\subsection{White Rabbit connector in front panel}

It has been detected in different boards (such as WR repetitors) that the
WR hole in the front pannel was not properly designed.\\

It seems that the current size and spacing of the WR connector is OK in V1,
however the issue is reported below:

\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue  450} & \url{http://www.ohwr.org/issues/450}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
           WR connector socket should be rechecked for better plugging quality.
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 450: WR connector in front panel}
  \end{center}
\end{table}

\subsection{Components not to be mounted}

\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue 501} & \url{http://www.ohwr.org/issues/501}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
          Resistor R98 should not be mounted.\\
          Resistor R137 should not be mounted.\\
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 501: not to be mounted resistors}
  \end{center}
\end{table}

\subsection{Protection for misconnections of the inputs}
A double control mechanism must be added in the FPGA to avoid damage in the
Blocking output stage.\\

\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue 503} & \url{http://www.ohwr.org/issues/503}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
         If the all the input channels of the board are connected to a high level and
         the RTM outputs are all parallel terminated to 50 Ohms the 24V power supply
         will blow up.
         
         To avoid this, some control must be added in the FPGA, first to detect and then to report via I2C. A protection fuse is currently not installed in the 12V
         rail. It's needed.\\
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 503: Protection for misconnections of the inputs}
  \end{center}
\end{table}

The proposal is to trigger event upon edge detection, and measure the level of
the inputs to report problems back through the I2C connection.\\

\pagebreak

\subsection{12 volts fuse to be added}

It was considered time ago. To be discussed in the meeting.

\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue 504} & \url{http://www.ohwr.org/issues/504}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
         After writing down a list of test to be performed, it was found that some
         configurations can harm the board.
         
         If all the inputs are connected to '1', the FPGA is programmed to generated a
         periodic signal of 3us with 50\% duty cycle. If all the outputs are terminated
         with 50 Ohms, irreversible damage will be caused to the 24V Power Supply.
         
         The power supply is able to provide 2.5 A (and up to 3.5A) in 24V. A fuse
         targeted to solve that problem must be placed in the 12V rail.\\
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 504: 12 volts fuse to be added}
  \end{center}
\end{table}

\subsection{Add silkscreen for fuses}
\begin{table}[!htb]
  \begin{center}
    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
    \begin{tabularx}{13cm}{|l|R|}
      \hline
      \textbf{OHWR issue 505} & \url{http://www.ohwr.org/issues/505}\\
      \hline
      \hline
      \multicolumn{2}{|l|}{
        \begin{minipage}[t]{0.95\columnwidth}%
        It should be added an easy to read silkscreen for every fuse in next V2
        board.\\
        \end{minipage}}\tabularnewline
      \hline
    \end{tabularx}
    \caption{Issue 505: add silkcreen for fuses}
  \end{center}
\end{table}


%\begin{table}[!htb]
%  \begin{center}
%    \newcolumntype{R}{>{\raggedleft\arraybackslash}X}%
%    \begin{tabularx}{13cm}{|l|R|}
%      \hline
%      \textbf{OHWR issue  } & \url{http://www.ohwr.org/issues/449}\\
%      \hline
%      \hline
%      \multicolumn{2}{|l|}{
%        \begin{minipage}[t]{0.95\columnwidth}%
%        a very long line a very long line a very long line a very long line
%        a very long line a very long line a very long line a very long line
%        a very long line a very long line a very long line %
%        \end{minipage}}\tabularnewline
%      \hline
%    \end{tabularx}
%    \caption{Issue }
%  \end{center}
%\end{table}

\end{document}
