High-Level Synthesis Code Generation for Transmit and Receive FIFO Registers

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This example shows how to generate High-Level Synthesis (HLS) code from MATLAB® code that models the data transfer between a transmit and receive first-in, first-out (FIFO) register or buffer. This example contains two functions that represent a receive FIFO buffer and a transmit FIFO buffer, and a test bench mlhdlc_fifo_tb that simulates the data transfer that occurs between the two buffers. Each function is hardware-ready and exhibits good practices and guidelines to follow when writing MATLAB functions to generate efficient HLS code. For more information on guidelines to follow, see Guidelines for Writing MATLAB Code to Generate Efficient HDL and HLS Code.

View Example Functions and Test Bench

You can set up the model and open the MATLAB design for the transmit FIFO and the receive FIFO.

type('mlhdlc_rx_fifo');

function [dout, empty, byte_ready, full, bytes_available] = ...
    mlhdlc_rx_fifo(get_byte, store_byte, byte_in, reset_fifo, fifo_enable)
%

%   Copyright 2014-2015 The MathWorks, Inc.

%
%  First In First Out (FIFO) structure.
%  This FIFO stores integers.
%  The FIFO is actually a circular buffer.
%
persistent head tail fifo byte_out handshake

if (reset_fifo || isempty(head))
    head = 1;
    tail = 2;
    byte_out = 0;
    handshake = 0;
end

if isempty(fifo)
    fifo = zeros(1,1024);
end

full = 0;
empty = 0;
byte_ready = 0;

% Section for checking full and empty cases
if ((tail == 1 && head == 1024) || ((head + 1) == tail))
    empty = 1;
end
if ((head == 1 && tail == 1024) || ((tail + 1) == head))
    full = 1;
end

% handshaking logic
if get_byte == 0
    handshake = 0;
end
if handshake == 1
    byte_ready = 1;
end

if (fifo_enable == 1)
    %%%%%%%%%%%%%%get%%%%%%%%%%%%%%%%%%%%%
    if (get_byte && ~empty && handshake == 0 )
        head = head + 1;
        if head == 1025
            head = 1;
        end
        byte_out = fifo(head);
        byte_ready = 1;
        handshake = 1;
    end
    %%%%%%%%%%%%%put%%%%%%%%%%%%%%%%%%%%%
    if (store_byte && ~full)
        fifo(tail) = byte_in;
        tail = tail + 1;
        if tail == 1025
            tail = 1;
        end
    end
end

% Section for calculating num bytes in FIFO
if (head < tail)
    bytes_available = (tail - head) - 1;
else
    bytes_available = (1024 - head) + tail - 1;
end
    
dout = byte_out;
end

type('mlhdlc_tx_fifo');

function [dout, empty, byte_received, full, bytes_available, dbg_fifo_enable] = ...
    mlhdlc_tx_fifo(get_byte, store_byte, byte_in, reset_fifo, fifo_enable)
%

%   Copyright 2014-2015 The MathWorks, Inc.

%
%  First In First Out (FIFO) structure.
%  This FIFO stores integers.
%  The FIFO is actually a circular buffer.
%
persistent head tail fifo byte_out handshake

if (reset_fifo || isempty(head))
    head = 1;
    tail = 2;
    byte_out = 0;
    handshake = 0;
end

if isempty(fifo)
    fifo = zeros(1,1024);
end

full = 0;
empty = 0;
byte_received = 0;

% Section for checking full and empty cases
if ((tail == 1 && head == 1024) || ((head + 1) == tail))
    empty = 1;
end
if ((head == 1 && tail == 1024) || ((tail + 1) == head))
    full = 1;
end

% handshaking logic
if store_byte == 0
    handshake = 0;
end
if handshake == 1
    byte_received = 1;
end

if (fifo_enable == 1)
    %%%%%%%%%%%%%%get%%%%%%%%%%%%%%%%%%%%%
    if (get_byte && ~empty)
        head = head + 1;
        if head == 1025
            head = 1;
        end
        byte_out = fifo(head);
    end
    %%%%%%%%%%%%%put%%%%%%%%%%%%%%%%%%%%%
    if (store_byte && ~full && handshake == 0)
        fifo(tail) = byte_in;
        tail = tail + 1;
        if tail == 1025
            tail = 1;
        end
        byte_received = 1;
        handshake = 1;
    end
end

% Section for calculating num bytes in FIFO
if (head < tail)
    bytes_available = (tail - head) - 1;
else
    bytes_available = (1024 - head) + tail - 1;
end

dout = byte_out;
dbg_fifo_enable = fifo_enable;
end

Open the MATLAB design for the test bench that exercises both designs. This test bench test both the transmit and receive FIFOs. However, when generating HLS code, because you have individual functions for the transmit and receive FIFOs, you need individual test benches to test both functions and generate code. For simulation purposes, you can use mlhdlc_fifo_tb, but for HLS code generation, use the receive FIFO test bench mlhdlc_rx_fifo_tb with the receive FIFO function mlhdlc_rx_fifo, and use the transmit FIFO test bench mlhdlc_tx_fifo with the transmit FIFO function mlhdlc_tx_fifo.

type('mlhdlc_fifo_tb');

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% simulation parameters
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% data payload creation

%   Copyright 2014-2015 The MathWorks, Inc.

messageASCII = 'Hello World!';
message = double(unicode2native(messageASCII));
msgLength = length(message);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% TX_FIFO core
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
numBytesToFifo = 1;
tx_get_byte = 0;
tx_full = 0;
tx_byte_received = 0;
i1 = 1;

while (numBytesToFifo <= msgLength && ~tx_full)
    % first thing the processor does is clear the internal tx fifo
    if i1 == 1
        tx_reset_fifo = 1;
        mlhdlc_tx_fifo(0, 0, 0, tx_reset_fifo, 1);
    else
        tx_reset_fifo = 0;
    end
    if (i1 > 1)
        tx_data_in = message(numBytesToFifo);
        numBytesToFifo = numBytesToFifo + 1;
        tx_store_byte = 1;
        while (tx_byte_received == 0)
            [tx_data_out, tx_empty, tx_byte_received, tx_full, tx_bytes_available] = ...
                mlhdlc_tx_fifo(tx_get_byte, tx_store_byte, tx_data_in, tx_reset_fifo, 1);
        end
        tx_store_byte = 0;
        while (tx_byte_received == 1)
            [tx_data_out, tx_empty, tx_byte_received, tx_full, tx_bytes_available] = ...
                mlhdlc_tx_fifo(tx_get_byte, tx_store_byte, tx_data_in, tx_reset_fifo, 1);
        end
    end
    i1 = i1 + 1;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Transfer Bytes from TX FIFO to RX FIFO
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
i1 = 1;

tx_get_byte = 0;
tx_store_byte = 0;
tx_data_in = 0;
tx_reset_fifo = 0;

rx_get_byte = 0;
rx_data_in = 0;
rx_reset_fifo = 0;

while (tx_bytes_available > 0)
        if i1 == 1
            rx_reset_fifo = 1;
            mlhdlc_rx_fifo(0, 0, 0, rx_reset_fifo, 1);
        else
            rx_reset_fifo = 0;
        end
        if (i1 > 1)
            tx_get_byte = 1;
            rx_store_byte = 1;
            [tx_data_out, tx_empty, tx_byte_received, tx_full, tx_bytes_available] = ...
                mlhdlc_tx_fifo(tx_get_byte, tx_store_byte, tx_data_in, tx_reset_fifo, 1);
            
            rx_data_in = tx_data_out;
            
            [rx_data_out, rx_empty, rx_byte_ready, rx_full, rx_bytes_available] = ...
                mlhdlc_rx_fifo(rx_get_byte, rx_store_byte, rx_data_in, rx_reset_fifo, 1);
        end
        i1 = i1 + 1;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% RX_FIFO core
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
numBytesFromFifo = 1;
rx_store_byte = 0;
rx_byte_received = 0;
i1 = 1;
msgBytes = zeros(1,msgLength);

while (~rx_empty)
    % first thing the processor does is clear the internal rx fifo
    if (i1 > 1)
        rx_get_byte = 1;
        while (rx_byte_ready == 0)
            [rx_data_out, rx_empty, rx_byte_ready, rx_full, rx_bytes_available] = ...
                mlhdlc_rx_fifo(rx_get_byte, rx_store_byte, rx_data_in, rx_reset_fifo, 1);
        end
        msgBytes(i1-1) = rx_data_out;
        rx_get_byte = 0;
        while (rx_byte_ready == 1)
            [rx_data_out, rx_empty, rx_byte_ready, rx_full, rx_bytes_available] = ...
                mlhdlc_rx_fifo(rx_get_byte, rx_store_byte, rx_data_in, rx_reset_fifo, 1);
        end
    end
    i1 = i1 + 1;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

numRecBytes = numBytesFromFifo;
if sum(msgBytes-message) == 0
    disp('Received message correctly');
else
    disp('Received message incorrectly');
end    
native2unicode(msgBytes)

Simulate the Design

Simulate the design with the test bench before generating code to ensure there are no runtime errors.

mlhdlc_fifo_tb

Received message correctly

ans =

    'Hello World!'

Create HDL Coder™ Project for the Receive FIFO

At the MATLAB command line, set up the path for HLS code generation by using the function hdlsetuphlstoolpath.

Create a HDL Coder project for the receive FIFO.

coder -hdlcoder -new mlhdlc_rx_fifo

Add the file mlhdlc_rx_fifo.m to the project as the MATLAB Function and mlhdlc_rx_fifo_tb.m as the MATLAB Test Bench and then click Workflow Advisor.

Generate HLS Code for the Receive FIFO

In the HDL Workflow Advisor, select MATLAB to HLS as the Code Generation Workflow and Cadence Stratus HLS as the Synthesis tool in Select Code Generation Target step.

Run all the steps from the beginning through the HLS code generation. Examine the generated HLS code for the receive FIFO by clicking the hyperlinks in the bottom pane.

For more information, see Get Started with MATLAB to High-Level Synthesis Workflow Using HDL Coder App.

Create HDL Coder Project for the Transmit FIFO

At the MATLAB command line, set up the path for HLS code generation by using the function hdlsetuphlstoolpath.

Create a HDL Coder project.

coder -hdlcoder -new mlhdlc_tx_fifo

Add mlhdlc_tx_fifo.m to the project as the MATLAB Function and mlhdlc_tx_fifo_tb.m as the MATLAB Test Bench and then click Workflow Advisor.

Generate HLS Code for the Transmit FIFO