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Great news for HxS developers: We are releasing version 1.0.16. In our ongoing commitment to security, we regularly maintain and update our dependencies. With this release, we are ensuring a robust and secure user experience. Please be aware that starting from this release, Java 17 or higher is a requirement.

In addition, we have dedicated efforts to enhance VHDL code integrity, systematically addressing syntax issues of the generated files. HxS 1.0.16 is now available in our download section.

Exciting news for HxS users: version 1.0.15 is here! This release focuses on improving VHDL code integrity, effectively fixing syntax issues across various HxS configurations. Explore these improvements — HxS 1.0.15 is now ready for you in our download section.

In this blog series, we will create a simple Intellectual Property (IP) core that calculates checksums, utilizing the HxS methodology for register interface description and the GateMate FPGA from Cologne Chip. Our experimental playground will be the GateMate Evaluation Board. The GateMate series brings us compact yet powerful FPGAs, perfect for a range of applications. Our focus will be on the CCGM1A1, equipped with 20,480 programmable elements, suitable for both combinatorial and sequential logic. This capacity is more than adequate for the CRC calculator we aim to create and explore in this article.

Register Interface

In this section, we dive into the world of HxS to craft a register interface. Taking inspiration from a practical example, we create a register interface for a CRC (Cyclic Redundancy Check) calculator, a crucial tool used in verifying the integrity of data in digital communications. We are basing our design on the same register interface as described in the ST Microelectronics reference manual (specifically, chapter 14 on page 336). It consists of the following registers:

• CRC data register (CRC_DR)
• CRC independent data register (CRC_IDR)
• CRC control register (CRC_CR)
• CRC initial value (CRC_INIT)
• CRC polynominal (CRC_POL)

Our HxS description begins with the specification of an interface. We aim for a 32-bit data bus width and an AXI4-Lite slave interface. Let's explore the HxS code that lays the foundation for our calculator:

    interface CrcCalculatorIfc
    {
        Name = "CRC Calculator Interface";
        DataBusWidth = 32;
        BusType = BusType.AXI4Lite;
        Blocks = [CrcCalculatorBlk];
    }
                

Here, we define the CrcCalculatorIfc interface. It's important to note that the address bus width adapts automatically to match the actual address space used by our IP, streamlining the design process.

Next, we create a block. In HxS, blocks are instrumental in grouping registers, bringing order and clarity to complex designs. For our CRC calculator, a single block suffices to house the five essential registers, mirroring the structure found in the ST Microelectronics reference manual:

    block CrcCalculatorBlk
    {
        Name = "CRC Calculator Block";
        Registers = [
            CRC_DR,
            CRC_IDR,
            CRC_CR,
            CRC_INIT(Offset=0x10),
            CRC_POL
        ];
    }
                

Each register in CrcCalculatorBlk starts at a specific offset, beginning at 0x0 and increasing sequentially. Notably, CRC_INIT begins at offset 0x10, followed by CRC_POL at 0x14. HxS auto-calculates offsets and addresses, simplifying the user's workload.

Now, let's define the registers within the CrcCalculatorBlock. The CRC_DR register, a special data register, is crucial as it receives data for CRC calculation and, upon read, provides the calculated CRC. This dual functionality is efficiently handled by the ReadTransparentWriteRegisterReg32 type.

    register CRC_DR : ReadTransparentWriteRegisterReg32
    {
        Name = "CRC Data Register";
        WriteRegisterPulse = true;
    }
                

Here, the extra write register pulse signals every new data input, triggering another CRC calculation.

The CRC_IDR is straightforward, functioning as a basic read/write register without additional complexities:

    register CRC_IDR : Reg32
    {
        Name = "CRC Independent Data Register";
    }
                

For controlling the CRC mechanism, we use the CRC_CR register. It enables control over various aspects of the CRC calculation:

    register CRC_CR : Reg32
    {
        Name = "CRC Control Register";
        Bits = [enum CrcControl
            {
                Values = [{
                        0 : value CrcControlReset { Width = 1; },
                        3 : value CrcPolySize { Width = 2; },
                        5 : value CrcReverseInputData { Width = 2; },
                        7 : value CrcReverseOutputData { Width = 1; }
                    }];
            }];
    }
                

CRC_INIT and CRC_POL registers provide the initial value and polynomial for the CRC calculation, respectively. The CRC_POL is set to a constant value to support the CRC-32 Ethernet polynomial 0x4C11DB7.

    register CRC_INIT : Reg32
    {
        Name = "CRC Initial Value";
    }

    register CRC_POL : ReadTransparentReg32
    {
        Name = "CRC Polynomial";
    }
                

With this compact yet powerful HxS description, we've laid the groundwork for a functional register interface. This approach demonstrates the ease and efficiency of prototyping with HxS. Our interface can now be iteratively refined and enriched with further details.

From this HxS description, we can generate the bus interface and comprehensive documentation in formats like Word, PDF, or HTML. Additionally, C header files facilitate embedded software integration.

Simulation

In this article, we focussed on an individual IP component rather than a complete FPGA design. Consequently, instead of creating a bitstream, we employ GHDL for simulation purposes. Our IP is simulated using the SimStm framework, a tool we developed for simulation and testing.

To begin with, we utilize the register description to generate various HxS artifacts, including the VHDL register interface and its documentation. For this process, we've set up a Linux environment, specifically using Ubuntu 22.04. The first step involves installing Ant.

    ~$ sudo apt-get install ant -y
                

Next, we clone the actual crc-calculator repository from the Eccelerators GitHub repository:

    ~$ git clone --recurse-submodules git@github.com:eccelerators/crc-calculator.git
                

Following that, we establish a Python3 virtual environment and install the necessary dependencies:

    ~$ python3 -m venv .venv
    ~$ source .venv/bin/activate
    ~$ pip3 install -r requirements.txt
                

With the setup complete, we are now ready to build all the artifacts required for simulation:

    ~$ make
                

The HxS files are located in the hxs directory. The VHDL files related to the IP and its simulation are organized within the following directory structure:

• src/vhdl This folder contains the primary VHDL source files for the IP.
• src-gen/vhdl Here, you'll find generated VHDL files specific to the AXI4-Lite interface.
• tb/vhdl This directory houses the VHDL files used for testbenching and simulation.

Additionally, the documentation for this IP, generated in various formats, is located in these folders:

• src-gen/docbook-pdf Contains the documentation in PDF format.
• src-gen/docbook-html Holds the HTML version of the documentation (Docbook).
• src-gen/html-sphinx Holds the HTML version of the documentation (Sphinx).
• src-gen/rst Stores the reStructuredText (rst) files, typically used for more textual documentation.

The simulation is executed with the following command:

    ~$ make sim
                

A successful simulation will yield an output similar to this:

    + ./crccalculatortestbench --stop-time=100000ns
    simstm/src/tb_simstm.vhd:1245:21:@1000300ps:(assertion note): test finished with no errors!!
                

Next Steps

In this overview, we have outlined our process of using HxS to prototype a register description for a CRC calculator IP. We successfully created all the necessary artifacts for VHDL simulation and synthesis. As our current scope is limited to the IP component without a complete FPGA design, we focused exclusively on simulating the design. This allowed us to test and validate the IP in isolation.

In a forthcoming article, we plan to delve deeper into the specifics of how we use SimStm, our proprietary simulation framework. This exploration will provide insights into the methodologies and advantages of using SimStm for IP simulation.

Looking ahead, another article will explore the creation of a complete FPGA design for the GateMate FPGA. This will include the synthesis process and bitstream creation for the GateMate Evaluation Board. This future work aims to bring our IP from simulation to a tangible, functioning component in a real-world FPGA environment.

We are excited to unveil the newest iteration of HxS. This release brings enhancements to VHDL code's quality, addressing and fixing potential syntax errors in various HxS code configurations. Experience the improvements firsthand — HxS 1.0.14 is now available in our download section.

Get ready to explore the latest release of HxS, version 1.0.13! Download it now and uncover a host of enhancements and bug fixes that promise an even smoother experience.

• References and Scope Enhancements
• Set Default Data Bus Width to 32
• Auto-Calculation of Address Bus Width
• Derive Alignment from Data Bus Width
• Fixed Asynchronous Read-Only / Write-Only Register Bug
• Eclipse Plugin and VS Code Extension

References and Scope Enhancements

Now, you can refer to objects from the same or outer scopes without the need for their fully qualified names. When looking up a reference, the first object found is used, starting from the reference's scope and going up to the outer scope.

    interface MyInterface
    {
        block MyBlock
        {
            Registers = [MyRegister];

            register MyRegister {} // Hides MyRegister of outer scope
        }

        register MyRegister {} // Is hidden for MyBlock.Registers
    }
                

This makes the code cleaner and more concise, as it is possible to reference objects directly without specifying their full paths each time.

Set Default Data Bus Width to 32

In this update, we have introduced a breaking change by transitioning the default data bus width from 8 to 32 bits. This modification may require adjustments in existing HxS descriptions.

    interface MyInterface
    {
        DataBusWidth = 32; // Defaults to 32-bits and can be left out
    }
                

Auto-Calculation of Address Bus Width

In our continuous pursuit of user comfort, we have introduced an automated calculation for the Interface.AddressBusWidth property. Now, if no specific value is provided, it derives the value from the blocks, eliminating the need for manual adjustments.

    interface MyInterface
    {
        AddressBusWidth = 8; // Is calculated and can be left out
    }
                

Derive Alignment from Data Bus Width

The Alignment property of the Block object now determines the address alignment of contiguous registers in bytes by deriving its value from the DataBusWidth property of the associated Interface object. Given the default DataBusWidth of 32-bits, the alignment's default value is set to 4 bytes.

    interface MyInterface
    {
        DataBusWidth = 32;
    }

    block MyBlock
    {
        Alignment = 4; // Is calculated and can be left out
        Registers = [
            MyRegister0,
            MyRegister1,
            MyRegister2
        ]
    }
                

Fixed Asynchronous Read-Only / Write-Only Register Bug

Previously, defining a register as asynchronous with exclusively readable or writable bit fields could inadvertently trigger the generation of corresponding read or write parts using properties like ReadAckDelay or WriteAckDelay. This resulted in incorrect register interface behavior. We've addressed this issue, ensuring proper functionality, and now provide clear information that such properties have no effect and will be ignored.

    register MyRegister
    {
        Async = true;
        ReadAckDelay = 3;
        WriteAckDelay = 3;
        Bits = [MyData];
    }

    data MyData
    {
        Width = 32;
        Behaviour = BitBehaviour.Constant;
    }
                

Eclipse Plugin and VS Code Extension

With every release, we ensure the HxS Eclipse plugin and VS Code extension are up-to-date. You can find both IDE integrations ready for download here.

We are excited to unveil HxS 1.0.12. It is now available for download. Discover a range of exciting new features such as AXI4-Lite support and improvements for IP-XACT.

• AXI4-Lite
• IP-XACT VHDL Wrapper
• Bus Reset Objects
• SPI Controller Example
• Eclipse Plugin and VS Code Extension

AXI4-Lite

After months of development and verification we added our third bus interface AXI4-Lite. Setting the BusType property of an interface to BusType.AXI4Lite is enough to create an AXI4-Lite register interface.

    interface MyInterface
    {
        BusType = BusType.AXI4Lite;
    }
                

An AXI4-Lite HxS example can be found at the playground.

IP-XACT VHDL Wrapper

We always strive to reduce complexity and to keep tedious work away from developers. Therefore, we introduced the vhdl.ipxact.wrapper annotation. It instructs the VHDL generater to create a VHDL entity without any records for use by IP-XACT. The annotation is part of an interface object and can be used as follows.

    @Generator('vhdl.ipxact.wrapper', 'true')
    interface MyInterface { }
                

Bus Reset Objects

We added the following bus reset objects to the HxS Base Library:

• BusReset.None - Bit field is not affected by bus reset
• BusReset.Sync - Bit field is affected by synchronous bus reset
• BusReset.Async - Bit field is affected by asynchronous bus reset

A developer might refer to an own reset object or make use of an exising one as in the following example. Note that the first reset represents the bus reset by convention. Resets specified after the bus reset add an additional signal to the bus interface.

    data MyData
    {
        Width = 4;
        Resets = [
            BusReset.None,
            MySoftReset0,
            MySoftReset1
        ];
    }
                

The dictionary syntax can be used as well. It enhances the readability if multiple resets are defined. Here is an example:

    data MyData
    {
        Width = 4;
        Resets = {
            0xU : BusReset.None,
            0x5 : MySoftReset0,
            0xF : MySoftReset1
        };
    }
                

Further information about the reset behaviour can be found in the documentation of the data and enum objects.

SPI Controller Example

In addition to the smaller examples at the playground, we continuously add practical examples to our the publicly available repository at GitHub. This time we added a SPI controller example, which shows advanced features of HxS.

Eclipse Plugin and VS Code Extension

We update the HxS Eclipse plugin and VS Code extension with each release. Both IDE integrations are available at the download section.

Great news! HxS 1.0.11 is now available for download. Discover a range of exciting new features and improvements.

• Added IP-XACT Extension
• Added Annotation for Identifier Customization
• Added a Playground
• Added Example Projects on GitHub
• Fixed Synchronous Registers with Asynchronous Properties

Added IP-XACT Extension

In order to improve our efforts for making HxS even more useful we added the IP-XACT extension. It can be used as follows:

    ~$ hxsc -o src-gen ipxact src/MyInterface.hxs
                

The IP-XACT extension supports the standards spirit._1685_2009, and accellera._1685_2014. By default, the extension generates IP-XACT files compliant to the accellera._1685_2014 standard. It can be changed using an annotation for the interface.

    @Generator('ipxact.standard', 'spirit._1685_2009')
    interface MyInterface { }
                

We are eager to improve the IP-XACT extension with each future release, so if you have any ideas how we might improve let us know.

Added Annotation for Identifier Customization

The VHDL, Python and C generators support the {vhdl, python, c}.naming.scope annotation to influence the creation of identifers. By default, generators create identifiers that are unique and short in length. Depending on the use case, it might be necessary to customize the creation of identifers. The annotation can be used as follows:

    @Generator('vhdl.naming.scope', 'interface')
    interface MyInterface
    {
        Blocks = [MyBlock];
    }

    block MyBlock
    {
        Registers = [MyRegister];
    }

    register MyRegister
    {
        Bits = [MyData];
    }

    data MyData
    {
        Width = 8;
    }
                

The example above will create the following identifiers for the VHDL package. The parts that are bold are influenced by the annotation.

    constant MYINTERFACE_MYBLOCK_BASE_ADDRESS : std_logic_vector(31 downto 0) := x"00000000";
    constant MYINTERFACE_MYBLOCK_SIZE : std_logic_vector(31 downto 0) := x"00000001";

    constant MYINTERFACE_MYBLOCK_MYREGISTER_WIDTH : integer := 8;
    constant MYINTERFACE_MYBLOCK_MYREGISTER_ADDRESS : std_logic_vector(31 downto 0) := std_logic_vector(x"00000000" + unsigned(MYINTERFACE_MYBLOCK_BASE_ADDRESS));

    constant MYINTERFACE_MYBLOCK_MYREGISTER_MYDATA_MASK : std_logic_vector(7 downto 0) := x"FF";
                

Using the interface scope will create the longest identifers, but ensures uniqueness. Further details and examples can be found in the documentation.

Added a Playground

In order to get to know HxS and its capabilities, we have created a playground that shows small examples of register interfaces and their corresponding HxS compiler output. The playground can be found here.

Example Projects on GitHub

In addition to our playground that provides small examples for learning purposes, we continuously work on repositories on GitHub offering practical examples.

• Interrupt Controller
• SPI Controller
• Double Buffer Controller
• Event Catcher

Fixed Synchronous Registers with Asynchronous Properties

If a register has been defined as synchronous, but has asynchronous properties like AsyncClk, AsyncRst, ReadAckDelay or WriteAckDelay, the generator has not ignored them. This lead to invalid VHDL code and has been fixed in this release. In addition, a warning is shown in case a register mixes synchronous and asynchronous properties.

    register MyRegister
    {
        Async = false; // Default value
        AsyncClk = "MyAsyncClkSignalName"; // Is ignored, because Async = false
        AsyncRst = "MyAsyncRstSignalName"; // Is ignored, because Async = false
        ReadAckDelay = 3; // Is ignored, because Async = false
        WriteAckDelay = 3; // Is ignored, because Async = false
    }
                

We are happy to release HxS 1.0.10. It comes with a bunch of new features and is available at our download section.

• Added annotations for VHDL comments
• Added HxS release version to CLI
• Added VS Code content assist and documentation

Added annotations for VHDL comments

We added annotations to activate Doxygen comments for the VHDL code generation. There are three possible options; none, brief and detailed. none is the default option and disables the generation of Doxygen comments. brief adds a short description and detailed a detailed description to the generated VHDL code. The following example shows how to activate Doxygen comments for the VHDL generator:

    @Generator('vhdl.comments.doxygen', 'detailed')
    interface MyInterface
    {
        Name = 'MyInterface';
        Description = 'My interface description.';
        Blocks = [MyBlock];
    }
                

It is important to note that comments are only provided for the generated VHDL package. For further information about annotations, please refer to the HxS Annotations documentation.

Added HxS release version to CLI

In order to improve the version management, we added the HxS release version in addition to the HxS compiler version to the command line interface. It can be accessed using the --version option.

    HxS 1.0.10
    HxS Compiler 1.0.16-502deb34
    Copyright (C) 2023 Eccelerators GmbH
                

To list the versions of all installed HxS extensions, the --extensions option can be used.

    Extensions Path: /home/developer/.hxs/extensions

    Extensions:

    C (c) 1.0.21-830987e7
    Docs (docs) 1.0.15-803f34cc
    Python (python) 1.0.4-f55ac08b
    simstm (simstm) 1.0.9-e0eeca02
    VHDL (vhdl) 1.0.18-dc735325
                

Added VS Code content assist and documentation

We continuously improve the usability of HxS. In this release, we focused on the VS Code extension. The extension is now able to provide content assist and documentation for HxS objects. The latest VS Code extension is available at the Visual Studio Marketplace .

We are happy to release HxS 1.0.9. It comes with a bunch of new features and is available at our download section.

• Added CLI Error Codes to HxS Compiler
• Changed Default Behaviour for Asynchronous Registers
• Added Snake Case Support to VHDL
• Highlight Bus Reset in Eclipse

Added CLI Error Codes to HxS Compiler

In order to check error conditions of the HxS compiler, we added error codes to the CLI application. The following error codes are available:

• 0 - No error
• 1 - Unknown error
• 2 - Input file or path not found
• 3 - Invalid license file
• 4 - Unknown extension error
• 5 - Input file validation error

It is important to note that the HxS compiler always exits gracefully logging detailled error information to the log file.

Changed Default Behaviour for Asynchronous Registers

In order to simplify the usage of asynchronous registers, the default behaviour has been changed. From now on, the asynchronous feedback acknowledge is used as default for both read and write acknowledge signals. This behaviour is overriden by an external acknowledge or delay. In order to use another acknowledge signal, the ReadExternalAck or WriteExternalAck property has to be used. The following example shows how to use an external acknowledge signal and acknowledge delay instead of an asynchronous feedback:

    register MyRegister
    {
        Async = true;
        ReadExternalAck = true;
        WriteAckDelay = 3;
        Bits = [MyData];
    }
                

Added Snake Case Support to VHDL

In order to support different naming conventions, the VHDL generator now supports snake case. The following example shows how to use snake case for the VHDL generator:

    @Generator('vhdl.letter_case', 'snake_case')
    interface MyInterface
    {
        DataBusWidth = 32;
        AddressBusWidth = 32;
        Blocks = [MyBlock];
        BusType = BusType.Avalon;
    }
                

Highlight Bus Reset in Eclipse

The first reset in a data or enum object's Resets list determines the bus reset. In order to emphasize the special meaning, we now highlight the bus reset in Eclipse and provide additional information. The following examples shows a data object with bus reset and additional reset signal:

    data MyData
    {
        Resets = [
            MyBusReset,
            MyAdditionalReset
        ];
    }
                

Further information about the reset behaviour can be found in the documentation of the data and enum objects. The latest Eclipse plugin is available at our download section.

We are happy to release HxS 1.0.8. It comes with a bunch of new features and is available at our download section.

• Added Avalon Bus Interface
• Added Python Extension
• Added --format / -f option to HxS Compiler CLI

Added Avalon Bus Interface

It is now possible to switch between Wishbone and Avalon bus interfaces. Therefore, we added a new property named BusType to the interface object. Setting BusType.Avalon will create a bus interface for Avalon as can be seen below.

    namespace MyNamespace
    {
        interface MyInterface
        {
            BusType = BusType.Avalon;
        }
    }
                

The following entity will be created providing AvalonDown and AvalonUp records for the bus connection.

    entity MyInterfaceAvalon is
        port (
            Clk : in std_logic;
            Rst : in std_logic;
            AvalonDown : in T_MyInterfaceAvalonDown;
            AvalonUp : out T_MyInterfaceAvalonUp;
            Trace : out T_MyInterfaceTrace; -- optional
            Selects : in T_MyInterfaceSelects; -- optional
            MyInterfaceBlockDown : out T_MyInterfaceBlockDown; -- optional
            MyInterfaceBlockUp : out T_MyInterfaceBlockUp -- optional
        );
    end;
                

Have a look at the Interface section of our documentation for further information.

Added Python Extension

In addition to the C extension we added a Python extension that generates variables for addresses, offsets, sizes and masks making the code more readable and enhancing the productivity of Python users.

    ~$ hxsc -o src-gen-python python src/MyInterface.hxs
                

Added --format / -f option to HxS Compiler CLI

In addition to use the auto-formatter of our IDE plugins it is now possible to use the hxsc CLI tool to format HxS files. This is especially useful for CI / CD pipelines or pre-commit hooks in order to enforce auto-formatting of HxS files.

    ~$ hxsc --format src/MyInterface.hxs
                

We are happy to release HxS 1.0.7. It comes with a bunch of new features and is available at our download section.

• Added external Acknowledge Signals
• Added Feedback for Asynchronous Acknowledge
• Added Content Assist to HxS Extension for VS Code
• Fixed Multi-File References of HxS Plugin for Eclipse

Added external Acknowledge Signals

Registers can now have external acknowledge signals for read or write accesses. They are enabled using the ReadExternalAck or WriteExternalAck properties. Further information is available in our documentation of Registers.

    namespace MyNamespace
    {
        register MyRegister
        {
            ReadExternalAck = true;
            WriteExternalAck = true;
        }
    }
                

Added Feedback for Asynchronous Acknowledge

It is now possible to specify whether to feedback the acknowledge signal for asynchronous read or write accesses.

    namespace MyNamespace
    {
        @Generator('vhdl.use_async_read_ack_feedback', 'true')
        @Generator('vhdl.use_async_write_ack_feedback', 'true')
        register MyRegister
        {
            ReadExternalAck = true;
            WriteExternalAck = true;
        }
    }
                

Added Content Assist to HxS Extension for VS Code

We continuously improve the HxS extension for VS Code. This time we implemented the content assist feature, so that properties of HxS objects are shown in the editor.

Fixed Multi-File References of HxS Plugin for Eclipse

We fixed a bug were the HxS plugin for Eclipse was unable to resolve references to HxS objects located in different files.