\documentclass[border=10pt]{standalone}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage{tikz}
\usetikzlibrary{
    shapes.geometric,
    arrows.meta,
    positioning,
    fit,
    calc
}

% Стили по ГОСТ 19.701-90
\tikzset{
    startstop/.style={
        rectangle,
        rounded corners,
        minimum width=3cm,
        minimum height=1cm,
        text centered,
        draw=black,
        fill=white,
        font=\bfseries
    },
    process/.style={
        rectangle,
        minimum width=3cm,
        minimum height=1.5cm,
        text centered,
        draw=black,
        fill=white,
        font=\bfseries
    },
    decision/.style={
        diamond,
        minimum width=3cm,
        minimum height=1cm,
        text centered,
        draw=black,
        fill=white,
        font=\bfseries
    },
    io/.style={
        trapezium,
        trapezium left angle=70,
        trapezium right angle=110,
        minimum width=3cm,
        minimum height=1cm,
        text centered,
        draw=black,
        fill=white,
        font=\bfseries
    },
    arrow/.style={
        thick,
        ->,
        >=Latex
    },
    dashed_box/.style={
        draw,
        dashed,
        inner sep=5mm
    }
}

\begin{document}

\begin{tikzpicture}[node distance=2cm]
    % Блоки памяти
    \node (memA) [process] {MemA};
    \node (memB) [process, below=of memA, yshift=-1cm] {MemB};
    \node (control) [process, below=of memB, yshift=-0.5cm] {Control};

    % Блоки обработки
    \node (multiplier) [process, right=4cm of memA, yshift=-0.75cm] {Multiplier};
    \node (accumulator) [process, right=of multiplier] {Accumulator};

    % Пунктирные рамки групп
    \node (group1) [dashed_box, fit=(memA)(memB)] {};
    \node (group2) [dashed_box, fit=(multiplier)(accumulator)] {};
    \node (group3) [dashed_box, fit=(control), inner sep=5mm, yshift=-5mm] {};

    % Стрелки
    \draw [arrow, line width=2pt] (memA.east) -- ++(1,0) |-
        node[pos=0.25, above] {Aij} (multiplier.west);
    \draw [arrow, line width=2pt] (memB.east) -- ++(1,0) |-
        node[pos=0.25, below] {Bjk} (multiplier.west);

    \draw [arrow] (multiplier.east) -- (accumulator.west);
    \draw [arrow] (accumulator.east) -- ++(2,0);

    \draw [arrow] (control.north) -- (memB.south);
    \draw [arrow] (control.east) -| (multiplier.south);
    \draw [arrow] (control.east) -| (accumulator.south);

    % Выход из аккумулятора
    \node[right=0.5cm of accumulator.east] {I};
\end{tikzpicture}

\end{document}