coder.hdl.constrainlatency

Specify the minimum and maximum acceptable hardware latency for a MATLAB function for SystemC code generation

Syntax

coder.hdl.constrainlatency(minimum_latency, maximum_latency)

Description

coder.hdl.constrainlatency(minimum_latency, maximum_latency) pragma is created that enables the user to specify the desired hardware latency range for a block of code for SystemC code generation.

Examples

Constrain the latency of the block of code within the specified range

Consider the MATLAB functions hdltest and region1. The latency of the region1 function is constrained between 0 and 2 clock cycles in the generated SystemC code.

function y = hdltest(a,b)
    u = a+8;
    v = b+6;
    y = region1(u,v);
end

function z = region1(a,b)
    % Optional comment between function defination and pragma
    coder.hdl.constrainlatency(0,2);
    m = a+1;
    n = b+2;
    z = m*n;
end

The following is the generated SystemC code.

#pragma once

#include "rtwtypes.hpp"

class hdltestClass
{
    public: 
    int8_T hdltest(int8_T a,int8_T b)
    {
        int8_T y;
        int8_T u;
        int8_T v;
        int8_T m;
        int8_T n;
        u = (sc_fixed<8,8,SC_TRN,SC_SAT>)((sc_int<9>)a + sc_int<9>(8.0));
        v = (sc_fixed<8,8,SC_TRN,SC_SAT>)((sc_int<9>)b + sc_int<9>(6.0));

    {
        /* Optional comment between function defination and pragma */
        HLS_CONSTRAIN_LATENCY(0,2,"region1");
        m = (sc_fixed<8,8,SC_TRN,SC_SAT>)((sc_int<9>)u + sc_int<9>(1.0));
        n = (sc_fixed<8,8,SC_TRN,SC_SAT>)((sc_int<9>)v + sc_int<9>(2.0));
        y = (sc_fixed<8,8,SC_TRN,SC_SAT>)(m*n);
    }

    return y;
    }
};

Input Arguments

minimum_latency — Minimum latency of the MATLAB^® function

positive integer

Minimum latency, specified as a positive integer.

Example: 4

maximum_latency — Maximum latency of the MATLAB function

positive integer

Maximum latency, specified as a positive integer.

Example: 10

Version History

Introduced in R2022a