Generate HDL and HLS Code from a Bisection Square Root Algorithm

R2026b

This example shows how to generate HDL and HLS code from a MATLAB® function that computes the square root of an unsigned fixed-point number using a pipelined bisection algorithm.

The bisection method finds the square root by guessing bits of the solution one at a time, from most significant to least significant. Each stage sets one bit and keeps it only if the squared candidate does not exceed the input. The design pipelines these stages so that it produces one result per clock cycle after an initial latency equal to the input word length. Because the design operates directly on fixed-point data, it does not require floating-point to fixed-point conversion.

Examine the MATLAB Design and Test Bench

Set up the MATLAB function and test bench for this example. In the MATLAB Command Window, enter:

mlhdlc_demo_setup("mlhdlc_sqrt");
This command opens a temporary working folder with the files required to run this example. The folder includes these files:

  • MATLAB function

  • Test bench

  • <model>_runme.m script, which includes the commands to generate HDL code

  • <model>_runme_hls.m script, which includes the commands to generate HLS code

The MATLAB function, mlhdlc_sqrt, computes the square root of unsigned fixed-point inputs by pipelining the bisection algorithm. The function uses persistent variables to maintain pipeline state and produces one result per clock cycle after an initial filling latency.

To view the function, enter:

open mlhdlc_sqrt.m;

The test bench file, mlhdlc_sqrt_tb, verifies the behavior of the MATLAB function by feeding random unsigned fixed-point values through the pipeline and comparing the output against the floating-point square root. It plots the absolute error to confirm numerical accuracy. To view the test bench, enter:

open mlhdlc_sqrt_tb.m;

Simulate the Design

To check for run-time errors, simulate the design by running the test bench. In the MATLAB Command Window, enter:

mlhdlc_sqrt_tb;

Generate HDL Code

The mlhdlc_sqrt_runme script specifies the target files, enables the settings required for this example, and generates HDL code.

The script specifies the MATLAB function and test bench, then creates a fixed-point configuration object and an HDL configuration object by using the coder.config function. It associates the test bench with both configuration objects.

designName = "mlhdlc_sqrt";
designTB = "mlhdlc_sqrt_tb";
fixptCfg = coder.config("fixpt");
fixptCfg.TestBenchName = designTB;
cfg = coder.config("hdl");
cfg.TestBenchName = designTB;

The script then generates code:

codegen("-float2fixed", "fixptCfg", "-config", "cfg", designName, ...
"-launchreport");

Run the Script

First, modify the mlhdlc_sqrt_runme script. Synthesis is disabled by default. Change the value for the SynthesizeGeneratedCode property:

cfg.SynthesizeGeneratedCode = true;

Update the settings for your synthesis tool:

cfg.SynthesisTool = "Xilinx Vivado";
cfg.SynthesisToolChipFamily = "Artix7";
cfg.SynthesisToolDeviceName = "xa7a100t";
cfg.SynthesisToolPackageName = "csg324";
cfg.SynthesisToolSpeedValue = "-1I";

Then, generate code by running the script:

mlhdlc_sqrt_runme

After code generation completes, the report opens. Examine the generated HDL code in the report.

Generate HLS Code

The mlhdlc_sqrt_runme_hls script specifies the target files, enables the settings required for this example, and generates HLS code.

The script specifies the MATLAB function and test bench, then creates a fixed-point configuration object and an HLS configuration object by using the coder.config function. It associates the test bench with both configuration objects.

designName = "mlhdlc_sqrt";
designTB = "mlhdlc_sqrt_tb";
fixptCfg = coder.config("fixpt");
fixptCfg.TestBenchName = designTB;

The script creates an HLS configuration object by using the coder.config function, associates the test bench, and enables simulation.

cfg = coder.config("hls");
cfg.TestBenchName = designTB;
cfg.GenerateHLSTestBench = true;
cfg.SimulateGeneratedCode = true;

The script then generates code:

codegen("-float2fixed", "fixptCfg", "-config", "cfg", designName, ...
"-launchreport");

Run the Script

First, modify the mlhdlc_sqrt_runme_hls script. Synthesis is disabled by default. Set the value for the SynthesizeGeneratedCode property to true:

cfg.SynthesizeGeneratedCode = true;

Depending on your synthesis tool, set one of these flags to true:

isCodingForStratusHLS = false;
isCodingForVitisHLS = true;

Depending on your synthesis tool, update these synthesis tool settings:

if isCodingForStratusHLS
    cfg.SynthesisTool = "Cadence Stratus HLS";
elseif isCodingForVitisHLS
    cfg.SynthesisTool = "Xilinx Vitis HLS";
    cfg.SynthesisToolChipFamily = "Artix7";
    cfg.SynthesisToolDeviceName = "xa7a100t";
    cfg.SynthesisToolPackageName = "csg324";
    cfg.SynthesisToolSpeedValue = "-1I";
end

Then, generate code by running the script:

mlhdlc_sqrt_runme_hls

After code generation completes, the report opens. Examine the generated HLS code in the report.

See Also

Functions

Topics