\input{preamble.tex}
\graphicspath{{images/2118-2128}{images}}

\title{2118 BNC-TTL / 2128 SMA-TTL}
\author{M-Labs Limited}
\date{January 2022}
\revision{Revision 2}
\companylogo{\includegraphics[height=0.73in]{artiq_sinara.pdf}}

\begin{document}
\maketitle

\section{Features}

\begin{itemize}
\item{8 TTL channels}
\item{Input- and output-capable}
\item{Galvanically isolated}
\item{3ns minimum pulse width}
\item{BNC or SMA connectors}
\end{itemize}

\section{Applications}

\begin{itemize}
\item{Photon counting}
\item{External equipment trigger}
\item{Optical shutter control}
\end{itemize}

\section{General Description}

The 2118 BNC-TTL card is an 8hp EEM module; the 2128 SMA-TTL is a 4hp EEM module. Both TTL cards add general-purpose digital I/O capabilities to carrier cards such as 1124 Kasli and 1125 Kasli-SoC.

Each card provides two banks of four digital channels for a total of eight digital channels, with respectively either BNC (2118) or SMA (2128) connecctors. Each bank possesses individual ground isolation. The direction (input or output) of each bank can be selected using DIP switches, and applies to all four channels of the bank.

Each channel supports 50\textOmega~terminations individually controllable using DIP switches. Outputs tolerate short circuits indefinitely.

Both cards are capable of a minimum pulse width of 3ns.

% Switch to next column
\vfill\break

\begin{figure}[h]
    \centering
    \scalebox{0.88}{
    \begin{circuitikz}[european, scale=0.95, every label/.append style={align=center}]

        \begin{scope}[yshift=1.3cm]

            \draw[color=white, text=black] (-0.1,0) node[twoportshape,t={IO 0}, circuitikz/bipoles/twoport/width=1.2, scale=0.4] (io0) {};
            \draw[color=white, text=black] (-0.1,-0.7) node[twoportshape,t={IO 1}, circuitikz/bipoles/twoport/width=1.2, scale=0.4 ] (io1) {};
            \draw[color=white, text=black] (-0.1,-1.4) node[twoportshape,t={IO 2}, circuitikz/bipoles/twoport/width=1.2, scale=0.4 ] (io2) {};
            \draw[color=white, text=black] (-0.1,-2.1) node[twoportshape,t={IO 3}, circuitikz/bipoles/twoport/width=1.2, scale=0.4 ] (io3) {};

            \node [label={[xshift=-0.18cm, yshift=-0.305cm]\tiny{IO 0}}] {};
            \node [label={[xshift=-0.18cm, yshift=-0.97cm]\tiny{IO 1}}] {};
            \node [label={[xshift=-0.18cm, yshift=-1.64cm]\tiny{IO 2}}] {};
            \node [label={[xshift=-0.18cm, yshift=-2.302cm]\tiny{IO 3}}] {};

            % draw female SMA_0,1,2,3
            \begin{scope}[scale=0.07 , rotate=-90, xshift=0cm, yshift=2cm]
                \draw (0,0.65) -- (0,3);
                \clip (-1.5,0) rectangle (1.5,1.5);
                \draw (0,0) circle(1.5);
                \clip (-0.8,0) rectangle (0.8,0.8);
                \draw (0,0) circle(0.8);
            \end{scope}
            \begin{scope}[scale=0.07 , rotate=-90, xshift=10cm, yshift=2cm]
                \draw (0,0.65) -- (0,3);
                \clip (-1.5,0) rectangle (1.5,1.5);
                \draw (0,0) circle(1.5);
                \clip (-0.8,0) rectangle (0.8,0.8);
                \draw (0,0) circle(0.8);
            \end{scope}
            \begin{scope}[scale=0.07 , rotate=-90, xshift=20cm, yshift=2cm]
                \draw (0,0.65) -- (0,3);
                \clip (-1.5,0) rectangle (1.5,1.5);
                \draw (0,0) circle(1.5);
                \clip (-0.8,0) rectangle (0.8,0.8);
                \draw (0,0) circle(0.8);
            \end{scope}
            \begin{scope}[scale=0.07 , rotate=-90, xshift=30cm, yshift=2cm]
                \draw (0,0.65) -- (0,3);
                \clip (-1.5,0) rectangle (1.5,1.5);
                \draw (0,0) circle(1.5);
                \clip (-0.8,0) rectangle (0.8,0.8);
                \draw (0,0) circle(0.8);
            \end{scope}

            \draw (1.6,-1.05) node[twoportshape,t={IO Bus Transceiver}, circuitikz/bipoles/twoport/width=2.5, scale=0.7, rotate=-90 ] (bus1) {};

            \draw (3.05,-0) node[twoportshape,t={Isolator}, circuitikz/bipoles/twoport/width=1.3, scale=0.4] (iso1) {};
            \draw (3.05,-0.7) node[twoportshape,t={Isolator}, circuitikz/bipoles/twoport/width=1.3, scale=0.4] (iso2) {};
            \draw (3.05,-1.4) node[twoportshape,t={Isolator}, circuitikz/bipoles/twoport/width=1.3, scale=0.4] (iso3) {};
            \draw (3.05,-2.1) node[twoportshape,t={Isolator}, circuitikz/bipoles/twoport/width=1.3, scale=0.4] (iso4) {};
            \draw (3.05,-2.7) node[twoportshape,t={Isolator}, circuitikz/bipoles/twoport/width=1.3, scale=0.4] (i2ciso1) {};

            \draw (4.5,-1.15) node[twoportshape,t=\fourcm{4-Channel LVDS}{Line Transceiver}, circuitikz/bipoles/twoport/width=2.6, scale=0.7, rotate=-90] (lvds1) {};

            \draw (6.8,-0.9) -- ++(0.00001,0) node[twoportshape, anchor=left, t={EEM port}, circuitikz/bipoles/twoport/width=6, scale=0.6, rotate=-90] (kasli) {} ;
            \draw (0.8,-3.5) node[twoportshape,t=\fourcm{Per-bank \phantom{spac} }{Input/Output Switch}, circuitikz/bipoles/twoport/width=2.7, scale=0.44] (ioswitch) {};
            \draw (3.05,-3.5) node[twoportshape,t=\fourcm{IO Expander}{for I2C Bus}, circuitikz/bipoles/twoport/width=1.8, scale=0.5] (i2c) {};

            \draw (5.68,-2.3) node[twoportshape,t=EEPROM, circuitikz/bipoles/twoport/width=1.2, scale=0.5] (eeprom) {};

            \draw (0.8,-2.7) node[twoportshape,t=\fourcm{High-Z/50\textOmega}{Switch \phantom{ssssss} }, circuitikz/bipoles/twoport/width=2, scale=0.4] (termswitch1) {};

            % Termination Switch 1,2,3,4
            \begin{scope}[xshift=0.9cm, yshift=-2.66cm, scale=0.12, every node/.style={scale=0.1}, rotate=-90 ]
                \draw (0.4,0) to[short,-o](0.75,0);
                \draw (0.78,0)-- +(30:0.46);
                \draw (1.25,0)to[short,o-](1.6,0);
            \end{scope}
            \begin{scope}[xshift=1cm, yshift=-2.66cm, scale=0.12, every node/.style={scale=0.1}, rotate=-90 ]
                \draw (0.4,0) to[short,-o](0.75,0);
                \draw (0.78,0)-- +(30:0.46);
                \draw (1.25,0)to[short,o-](1.6,0);
            \end{scope}
            \begin{scope}[xshift=1.1cm, yshift=-2.66cm, scale=0.12, every node/.style={scale=0.1}, rotate=-90 ]
                \draw (0.4,0) to[short,-o](0.75,0);
                \draw (0.78,0)-- +(30:0.46);
                \draw (1.25,0)to[short,o-](1.6,0);
            \end{scope}
            \begin{scope}[xshift=1.2cm, yshift=-2.66cm, scale=0.12, every node/.style={scale=0.1}, rotate=-90 ]
                \draw (0.4,0) to[short,-o](0.75,0);
                \draw (0.78,0)-- +(30:0.46);
                \draw (1.25,0)to[short,o-](1.6,0);
            \end{scope}

        \end{scope}

        % I/O Switch 1, 2
        \begin{scope}[xshift=1.2cm, yshift=-1.98cm, scale=0.12, every node/.style={scale=0.1}, rotate=-90 ]
            \draw (0.4,0) to[short,-o](0.75,0);
            \draw (0.78,0)-- +(30:0.46);
            \draw (1.25,0)to[short,o-](1.6,0);
        \end{scope}
        \begin{scope}[xshift=1.32cm, yshift=-1.98cm, scale=0.12, every node/.style={scale=0.1}, rotate=-90 ]
            \draw (0.4,0) to[short,-o](0.75,0);
            \draw (0.78,0)-- +(30:0.46);
            \draw (1.25,0)to[short,o-](1.6,0);
        \end{scope}

        \draw (0.8,-3.05) node[twoportshape,t=\fourcm{High-Z/50\textOmega}{Switch \phantom{ssssss} }, circuitikz/bipoles/twoport/width=2, scale=0.4] (termswitch2) {};

        % Termination Switch 5,6,7,8
        \begin{scope}[xshift=0.9cm, yshift=-3.02cm, scale=0.12, every node/.style={scale=0.1}, rotate=-90 ]
            \draw (0.4,0) to[short,-o](0.75,0);
            \draw (0.78,0)-- +(30:0.46);
            \draw (1.25,0)to[short,o-](1.6,0);
        \end{scope}
        \begin{scope}[xshift=1cm, yshift=-3.02cm, scale=0.12, every node/.style={scale=0.1}, rotate=-90 ]
            \draw (0.4,0) to[short,-o](0.75,0);
            \draw (0.78,0)-- +(30:0.46);
            \draw (1.25,0)to[short,o-](1.6,0);
        \end{scope}
        \begin{scope}[xshift=1.1cm, yshift=-3.02cm, scale=0.12, every node/.style={scale=0.1}, rotate=-90 ]
            \draw (0.4,0) to[short,-o](0.75,0);
            \draw (0.78,0)-- +(30:0.46);
            \draw (1.25,0)to[short,o-](1.6,0);
        \end{scope}
        \begin{scope}[xshift=1.2cm, yshift=-3.02cm, scale=0.12, every node/.style={scale=0.1}, rotate=-90 ]
            \draw (0.4,0) to[short,-o](0.75,0);
            \draw (0.78,0)-- +(30:0.46);
            \draw (1.25,0)to[short,o-](1.6,0);
        \end{scope}

        % channel 5,6,7,8
        \begin{scope}[yshift=-3.6cm]
            \draw[color=white, text=black]  (-0.1,0) node[twoportshape,t={IO 4}, circuitikz/bipoles/twoport/width=1.2, scale=0.4 ] (io4) {};
            \draw[color=white, text=black]  (-0.1,-0.7) node[twoportshape,t={IO 5}, circuitikz/bipoles/twoport/width=1.2, scale=0.4 ] (io5) {};
            \draw[color=white, text=black]  (-0.1,-1.4) node[twoportshape,t={IO 6}, circuitikz/bipoles/twoport/width=1.2, scale=0.4 ] (io6) {};
            \draw[color=white, text=black]  (-0.1,-2.1) node[twoportshape,t={IO 7}, circuitikz/bipoles/twoport/width=1.2, scale=0.4 ] (io7) {};

            \node [label={[xshift=-0.18cm, yshift=-0.305cm]\tiny{IO 4}}] {};
            \node [label={[xshift=-0.18cm, yshift=-0.97cm]\tiny{IO 5}}] {};
            \node [label={[xshift=-0.18cm, yshift=-1.64cm]\tiny{IO 6}}] {};
            \node [label={[xshift=-0.18cm, yshift=-2.302cm]\tiny{IO 7}}] {};

            % draw female SMA 4,5,6,7
            \begin{scope}[scale=0.07 , rotate=-90, xshift=0cm, yshift=2cm]
                \draw (0,0.65) -- (0,3);
                \clip (-1.5,0) rectangle (1.5,1.5);
                \draw (0,0) circle(1.5);
                \clip (-0.8,0) rectangle (0.8,0.8);
                \draw (0,0) circle(0.8);
            \end{scope}
            \begin{scope}[scale=0.07 , rotate=-90, xshift=10cm, yshift=2cm]
                \draw (0,0.65) -- (0,3);
                \clip (-1.5,0) rectangle (1.5,1.5);
                \draw (0,0) circle(1.5);
                \clip (-0.8,0) rectangle (0.8,0.8);
                \draw (0,0) circle(0.8);
            \end{scope}
            \begin{scope}[scale=0.07 , rotate=-90, xshift=20cm, yshift=2cm]
                \draw (0,0.65) -- (0,3);
                \clip (-1.5,0) rectangle (1.5,1.5);
                \draw (0,0) circle(1.5);
                \clip (-0.8,0) rectangle (0.8,0.8);
                \draw (0,0) circle(0.8);
            \end{scope}
            \begin{scope}[scale=0.07 , rotate=-90, xshift=30cm, yshift=2cm]
                \draw (0,0.65) -- (0,3);
                \clip (-1.5,0) rectangle (1.5,1.5);
                \draw (0,0) circle(1.5);
                \clip (-0.8,0) rectangle (0.8,0.8);
                \draw (0,0) circle(0.8);
            \end{scope}


            \draw (1.6,-1.05) node[twoportshape,t={IO Bus Transceiver}, circuitikz/bipoles/twoport/width=2.5, scale=0.7, rotate=-90 ] (bus2) {};

            \draw (3.05,-0) node[twoportshape,t={Isolator}, circuitikz/bipoles/twoport/width=1.3, scale=0.4] (iso5) {};
            \draw (3.05,-0.7) node[twoportshape,t={Isolator}, circuitikz/bipoles/twoport/width=1.3, scale=0.4] (iso6) {};
            \draw (3.05,-1.4) node[twoportshape,t={Isolator}, circuitikz/bipoles/twoport/width=1.3, scale=0.4] (iso7) {};
            \draw (3.05,-2.1) node[twoportshape,t={Isolator}, circuitikz/bipoles/twoport/width=1.3, scale=0.4] (iso8) {};
            \draw (3.05,0.6) node[twoportshape,t={Isolator}, circuitikz/bipoles/twoport/width=1.3, scale=0.4] (i2ciso2) {};

            \draw (4.5,-1.05) node[twoportshape,t=\fourcm{4-Channel LVDS}{Line Transceiver}, circuitikz/bipoles/twoport/width=2.6, scale=0.7, rotate=-90] (lvds2) {};

        \end{scope}

        % Drawing Connections
        \draw [latexslim-latexslim] (io0.east) -- ++(1,0);
        \draw [latexslim-latexslim] (io1.east) -- ++(1,0);
        \draw [latexslim-latexslim] (io2.east) -- ++(1,0);
        \draw [latexslim-latexslim] (io3.east) -- ++(1,0);
        \draw [latexslim-latexslim] (io4.east) -- ++(1,0);
        \draw [latexslim-latexslim] (io5.east) -- ++(1,0);
        \draw [latexslim-latexslim] (io6.east) -- ++(1,0);
        \draw [latexslim-latexslim] (io7.east) -- ++(1,0);

        \draw [latexslim-latexslim] (iso1.west) -- ++(-0.72,0) ;
        \draw [latexslim-latexslim] (iso2.west) -- ++(-0.72,0) ;
        \draw [latexslim-latexslim] (iso3.west) -- ++(-0.72,0) ;
        \draw [latexslim-latexslim] (iso4.west) -- ++(-0.72,0) ;
        \draw [latexslim-latexslim] (iso1.east) -- ++(0.69,0);
        \draw [latexslim-latexslim] (iso2.east) -- ++(0.69,0);
        \draw [latexslim-latexslim] (iso3.east) -- ++(0.69,0);
        \draw [latexslim-latexslim] (iso4.east) -- ++(0.69,0);

        \draw [latexslim-latexslim] (iso5.west) -- ++(-0.72,0) ;
        \draw [latexslim-latexslim] (iso6.west) -- ++(-0.72,0) ;
        \draw [latexslim-latexslim] (iso7.west) -- ++(-0.72,0) ;
        \draw [latexslim-latexslim] (iso8.west) -- ++(-0.72,0) ;
        \draw [latexslim-latexslim] (iso5.east) -- ++(0.7,0);
        \draw [latexslim-latexslim] (iso6.east) -- ++(0.7,0);
        \draw [latexslim-latexslim] (iso7.east) -- ++(0.7,0);
        \draw [latexslim-latexslim] (iso8.east) -- ++(0.7,0);

        \draw [latexslim-] (eeprom.south) -- ++(0,-0.95);

        \draw [latexslim-latexslim] (lvds1.north) -- ++(1.61,0);
        \draw [latexslim-latexslim] (lvds2.north) -- ++(1.62,0);
        \draw [latexslim-latexslim] (i2c.east) -- ++(2.77,0);
        \draw [latexslim-] (i2c.west) -- (ioswitch.east) ;

        \draw [-latexslim] (i2c.north east) -- (lvds1.south east);
        \draw [-latexslim] (i2c.south east) -- (lvds2.south west);

        \draw [-latexslim] (i2ciso1.west) -- (bus1.north east);
        \draw [thin] [-latexslim] (i2c.north) -- (i2ciso1.south);

        \draw [-latexslim] (i2ciso2.west) -- (bus2.north west);
        \draw [thin] [-latexslim] (i2c.south) -- (i2ciso2.north);


        % termination switch connection
        \draw (0.65,-1.18) -- ++(0,2.47) ;
        \draw (0.75,-1.18) -- ++(0,1.77) ;
        \draw (0.85,-1.18) -- ++(0,1.07) ;
        \draw (0.95,-1.18) -- ++(0,0.37) ;

        \draw (0.65,-3.25) -- ++(0,-2.45) ;
        \draw (0.75,-3.25) -- ++(0,-1.75) ;
        \draw (0.85,-3.25) -- ++(0,-1.05) ;
        \draw (0.95,-3.25) -- ++(0,-0.35) ;

        \node[draw, dotted, thick, rounded corners, inner xsep=0.7em, inner ysep=0.4em, fit=(io0) (i2ciso1.south west)] (box1) {};
        \node[fill=white, rotate=-90] at (box1.west) {GND BANK 1};
        \node[fill=white,above] at (box1.north) {\tiny{Either all 4 channels are inputs or all 4 channels are outputs }};


        \node[draw, dotted, thick, rounded corners, inner xsep=0.7em, inner ysep=0.4em, fit=(io4)(termswitch2) (iso8.south west)] (box2) {};
        \node[fill=white, rotate=-90] at (box2.west) {GND BANK 2};
        \node[fill=white,below] at (box2.south) {\tiny{Either all 4 channels are inputs or all 4 channels are outputs }};

    \end{circuitikz}
    }

    \caption{Simplified Block Diagram}
\end{figure}

\begin{figure}[hbt!]
    \centering
    \includegraphics[height=1.8in]{photo2118-2128.jpg }
    \caption{BNC-TTL and SMA-TTL cards}%
    \includegraphics[angle=90, height=0.7in]{DIO_BNC_FP.jpg}
    \includegraphics[angle=90, height=0.4in]{DIO_SMA_FP.jpg}
    \caption{BNC-TTL and SMA-TTL front panels}%
    \label{fig:example}%
\end{figure}

\onecolumn

\sourcesectiond{2118 BNC-TTL}{2128 SMA-TTL}{https://github.com/sinara-hw/DIO_BNC}{https://github.com/sinara-hw/DIO_SMA}

\section{Electrical Specifications}
All specifications are in $0\degree C \leq T_A \leq 70\degree C$ unless otherwise noted.
Specifications were derived based on the datasheets of the bus transceiver IC (SN74BCT25245DW\footnote{\label{transceiver}\url{https://www.ti.com/lit/ds/symlink/sn74bct25245.pdf}}) and the isolator IC (SI8651BB-B-IS1\footnote{\label{isolator}\url{https://www.skyworksinc.com/-/media/Skyworks/SL/documents/public/data-sheets/si865x-datasheet.pdf}}). The typical value of minimum pulse width is based on test results\footnote{\label{sinara187}\url{https://github.com/sinara-hw/sinara/issues/187}}.

\begin{table}[h]
\begin{threeparttable}
\caption{Recommended Operating Conditions}
\begin{tabularx}{\textwidth}{l | c c c | c | X}
    \thickhline
    \textbf{Parameter} & \textbf{Min.} & \textbf{Typ.} & \textbf{Max.} &
    \textbf{Unit} & \textbf{Conditions} \\
    \hline
    High-level input voltage\repeatfootnote{transceiver} & 2 & & 5.5* & V & \\
    \hline
    Low-level input voltage\repeatfootnote{transceiver} & -0.5 & & 0.8 & V & \\
    \hline
    Input clamp current\repeatfootnote{transceiver} & & & -18 & mA & termination disabled \\
    \hline
    High-level output current\repeatfootnote{transceiver} & & & -160 & mA & \\
    \hline
    Low-level output current\repeatfootnote{transceiver} & & & 376 & mA & \\
    \thickhline
    \multicolumn{6}{l}{*With the 50\textOmega~termination enabled, the input voltage should not exceed 5V.}
\end{tabularx}
\end{threeparttable}
\end{table}

\begin{table}[h]
\begin{threeparttable}
\caption{Electrical Characteristics}
\begin{tabularx}{\textwidth}{l | c c c | c | X}
    \thickhline
    \textbf{Parameter} & \textbf{Min.} & \textbf{Typ.} & \textbf{Max.} &
    \textbf{Unit} & \textbf{Conditions} \\
    \hline
    High-level output voltage\repeatfootnote{transceiver} & 2 &  &  & V & $I_{OH}$=-160mA \\
    & 2.7 &  &  & V & $I_{OH}$=-6mA \\
    \hline
    Low-level output voltage\repeatfootnote{transceiver} & & 0.42 & 0.55 & V & $I_{OL}$=188mA \\
    &  &  & 0.7 & V & $I_{OL}$=376mA \\
    \hline
    Minimum pulse width\repeatfootnote{isolator}\textsuperscript{,}\repeatfootnote{sinara187} & & 3 & 5 & ns & \\
    \hline
    Pulse width distortion\repeatfootnote{isolator} & & 0.2 & 4.5 & ns &  \\
    \hline
    Peak jitter\repeatfootnote{isolator} & & 350 & & ps &  \\
    \hline
    Data rate\repeatfootnote{isolator} & 0 & & 150 & Mbps & \\
    \thickhline
\end{tabularx}
\end{threeparttable}
\end{table}

Minimum pulse width was measured by generating pulses of progressively longer duration through a DDS generator and using them as input for a BNC-TTL card. The input BNC-TTL card was connected to another BNC-TTL card as output. The output signal is measured and shown in Figure \ref{fig:pulsewidth}.

\begin{figure}[ht]
    \centering
    \includegraphics[height=3in]{bnc_ttl_min_pulse_width.png}
    \caption{Minimum pulse width required for BNC-TTL card}
    \label{fig:pulsewidth}
\end{figure}

\newpage

The red trace shows the DDS generator input pulses. The blue trace shows the measured signal from the output BNC-TTL. Note that the first red pulse failed to reach the 2.1V threshold required by TTL and was not propagated. The first blue (output) pulse is the result of the second red (input) pulse, of 3ns width, which propagated correctly. 

\section{Configuring IO Direction \& Termination}

IO direction and termination must be configured by setting physical switches on the board. The termination switches are found on the middle-left and the IO direction switches on the middle-right of both cards. Termination switches select between high impedance (\texttt{OFF}) and 50\textOmega~(\texttt{ON}). Note that termination switches are by-channel but IO direction switches are by-bank. 

\begin{itemize}
    \itemsep0em
    \item IO direction switch closed (\texttt{ON}) \\
          Fixes the corresponding bank to output. The IO direction cannot be changed by I\textsuperscript{2}C.
    \item IO direction switch open (OFF) \\
          The corresponding bank is set to input by default. IO direction \textit{can} be changed by I\textsuperscript{2}C.
\end{itemize}

\begin{figure}[hbt!]
    \centering
    \subfloat[\centering BNC-TTL]{{
        \includegraphics[height=1.5in]{bnc_ttl_switches.jpg}
    }}%
    \subfloat[\centering SMA-TTL]{{
        \includegraphics[height=1.5in]{sma_ttl_switches.jpg}
    }}%
    \caption{Position of switches}%
\end{figure}

\newpage
\codesection{2118 BNC-TTL/2128 SMA-TTL cards}

Timing accuracy in these examples is well under 1 nanosecond thanks to ARTIQ RTIO infrastructure.

\subsection{One pulse per second}
The channel should be configured as output in both the gateware and hardware.
\inputcolorboxminted{firstline=9,lastline=14}{examples/ttl.py}

\subsection{Morse code}
This example demonstrates some basic algorithmic features of the ARTIQ-Python language.
\inputcolorboxminted{firstline=22,lastline=39}{examples/ttl.py}

\newpage
\subsection{Sub-coarse-RTIO-cycle pulse}
With the use of ARTIQ RTIO, only one event can be enqueued per \textit{coarse RTIO cycle}, which typically corresponds to 8ns. To emit pulses of less than 8ns, careful timing is needed to ensure that the \texttt{ttl.on()} \& \texttt{ttl.off()} event are submitted during different coarse RTIO cycles.

\inputcolorboxminted{firstline=60,lastline=64}{examples/ttl.py}

\subsection{Edge counting in a 1ms window}
The \texttt{TTLInOut} class implements \texttt{gate\char`_rising()}, \texttt{gate\char`_falling()} \& \texttt{gate\char`_both()} for rising edge, falling edge, both rising edge \& falling edge detection respectively.
The channel should be configured as input in both gateware and hardware. Invoke one of the 3 methods to start edge detection.
\inputcolorboxminted{firstline=14,lastline=15}{examples/ttl_in.py}
Input signal can generated from another TTL channel or from other sources. Manipulate the timeline cursor to generate TTL pulses using the same kernel.
\inputcolorboxminted{firstline=10,lastline=22}{examples/ttl_in.py}
The detected edges are registered to the RTIO input FIFO. By default, the FIFO can hold 64 events. The FIFO depth is defined by the \texttt{ififo\char`_depth} parameter for \texttt{Channel} class in \texttt{rtio/channel.py}.
Once the threshold is exceeded, an \texttt{RTIOOverflow} exception will be triggered when the input events are read by the kernel CPU.
Finally, invoke \texttt{count()} to retrieve the edge count from the input gate.

The RTIO system can report at most one edge detection event for every coarse RTIO cycle. In principle, to guarantee all rising edges are counted (with \texttt{gate\char`_rising()} invoked), the theoretical minimum separation between rising edges is one coarse RTIO cycle (typically 8 ns). However, both the electrical specifications and the possibility of triggering \texttt{RTIOOverflow} exceptions should also be considered.

\newpage
\subsection{Edge counting using \texttt{EdgeCounter}}
This example code uses a gateware counter to substitute the software counter, which has a maximum count rate of approximately 1 million events per second. If a gateware counter is enabled on the TTL channel, it can typically count up to 125 million events per second:
\inputcolorboxminted{firstline=31,lastline=36}{examples/ttl_in.py}
Edges are detected by comparing the current input state and that of the previous coarse RTIO cycle. Therefore, the theoretical minimum separation between 2 opposite edges is 1 coarse RTIO cycle (typically 8 ns).

\subsection{Responding to an external trigger}
One channel needs to be configured as input, and the other as output.
\inputcolorboxminted{firstline=45,lastline=51}{examples/ttl_in.py}

\subsection{62.5 MHz clock signal generation}
A TTL channel can be configured as a \texttt{ClockGen} channel, which generates a periodic clock signal. Each channel has a phase accumulator operating on the RTIO clock, where it is incremented by the frequency tuning word at each coarse RTIO cycle. Therefore, jitter should be expected when the desired frequency cannot be obtained by dividing the coarse RTIO clock frequency with a power of 2.

Typically, with the coarse RTIO clock at 125 MHz, a \texttt{ClockGen} channel can generate up to 62.5 MHz.

\inputcolorboxminted{firstline=72,lastline=75}{examples/ttl.py}

\newpage
\subsection{Minimum sustained event separation}
The minimum sustained event separation is the least time separation between input gated events for which all gated edges can be continuously \& reliabily timestamped by the RTIO system without causing \texttt{RTIOOverflow} exceptions. The following \texttt{run()} function finds the separation by approximating the time of running \texttt{timestamp\char`_mu()} as a constant. Import the \texttt{time} library to use \texttt{time.sleep()}.

\inputcolorboxminted{firstline=63,lastline=98}{examples/ttl_in.py}

\begin{center}
\begin{table}[H]
    \captionof{table}{Minimum sustained event separation of different carriers}
    \centering
    \begin{tabular}{|c|c|c|}
    \hline
    Carrier  & Kasli v1.1 & Kasli-SoC \\ \hline
    Duration & 650 ns     & 600 ns    \\ \hline
    \end{tabular}
    \end{table}
\end{center}

\ordersection{2118 BNC-TTL/2128 SMA-TTL}

\finalfootnote

\end{document}