“VHDL Interfaces and Example Designs for the XSV Board 1.0” is a collection of resources to be used with the XSV board v1.0, produced by XESS Corp. This board contains a Virtex FPGA from Xilinx Inc. and support circuitry for communicating with a wide variety of external devices. This set of resources is designed to provide a set of VHDL entities that act as interfaces to the various capabilities and devices on the XSV board, as well as sample designs that demonstrate the use of the board’s main features. The resources were developed internally by students at the University of Queensland, Australia. They are made publicly available in the hope that they may be of some help to others who are starting work on similar projects.

Most of these resources consist of VHDL source code and the accompanying documentation. For a list of the resources, see section 3.0, “List of designs”.

2.0 About this document

This Introduction and Overview serves as a summary of all the resources in this collection. It lists all the resources in the collection and provides information that is common to most of the designs. For example, the basic design flow used to synthesize and implement the VHDL source code is explained in this document.

3.0 List of designs

Most of resources in this collection can be grouped into the following two categories:

3.1 VHDL modules

These consist of VHDL entities that act as interfaces to the peripheral capabilities of the XSV board. These entities are designed to be embedded in a larger, arbitrary design, which will often be referred to as the “user” design. The VHDL modules are designed to make it easier for a user design to interact with the various external devices that can be attached to the XSV board (e.g. audio in/out, video in/out, Ethernet network connection).

Most VHDL modules also come with an accompanying stand-alone design that demonstrates the use of the module. The VHDL modules cannot be directly implemented on the Virtex FPGA without an accompanying top-level entity.

3.2 Stand-alone VHDL designs

These sets of VHDL source files always include a top-level entity. As such, stand-alone designs can be directly implemented on the Virtex FPGA and do not need to be incorporated in a larger user design. Stand-alone designs serve as examples of how to use the peripheral capabilities of the board. Many of the stand-alone designs include modules that can be used separately in a user’s own design.

Each stand-alone design comes with a UCF file that ensures it will be correctly implemented on the XSV board. Most of the constraints in these files are pin constraints.

3.3 Other designs

As well as modules and stand-alone designs, there is also a Visual Basic programme that accompanies one of the modules to provide communication between the XSV board and a PC.

3.4 List of designs

Design Name	Type	Explanation
VHDL IP Stack	Modules and stand-alone.	Uses the Ethernet PHY chip on the XSV board. Provides an implementation of Ethernet, IP and several transport protocols.
Audio Project	Modules and stand-alone.	Uses the stereo codec chip on the XSV board. Records data from the audio port and stores it in SRAM. Allows the recorded audio to be played back again.
VGA Interface	Modules and stand-alone.	Uses the RAMDAC and VGA monitor interface on the XSV board. Displays test patterns on a VGA monitor, using several different D/A conversion modes.
Video Input Project	Stand-alone only.	Uses the video decoder chip on the XSV board. Decodes RCA and S-Video signals into pixel data, which is stored in SRAM. This data is then sent to a VGA monitor.
SRAM Interface	Modules only.	Uses the two banks of SRAM provided on the XSV board. Provides a simpler synchronous interface to either bank of SRAM.
PC to SRAM Interface	Modules and stand-alone.	Uses the parallel port connections on the XSV board. Uses VHDL modules to allow a PC programme to read and write to any location of the XSV board’s SRAM through the parallel port. A Visual Basic utility programme that utilises these capabilities is also provided.
CPLD SVF File Descriptions	Stand-alone only.	A number of designs for the CPLD on the XSV board are provided. Most of these make only minor changes to the default design for the CPLD provided by XESS.
PS/2 Encoder/Decoder	Stand-alone only.	Uses the PS2 connections on the XSV board. Displays data received from a PS2 device and can send data to a PS2 device.

4.0 Development platform and tools

These resources have been developed using the following platforms and tools:

Item:	Details:	Company:
FPGA development board	XSV-300 v1.0 · Includes a Virtex xcv300-4-pq240 (300 000 gates, speed grade 4) from Xilinx Inc. · A standard ATX power supply was used.	XESS Corp.
PC Platform	Windows 98 (PII, 350MHz, 128 MB RAM)	Microsoft Corp.
Board configuration software	XSVTOOLs v3.2 · Virtex configuration was performed using the GXSLOAD tool using the parallel port.	XESS Corp.
VHDL design environment	Foundation F3.1i	Xilinx Inc.
PC software development	Microsoft Visual Basic v6.0 (as part of Microsoft Visual Studio)	Microsoft Corp.

5.0 Design flow for FPGA designs

This section explains the basic design flow used to synthesise and implement a VHDL stand-alone design for the Virtex FPGA. It is assumed that the reader is using the same development tools listed in section 4.0 of this document, but particularly that they are using Xilinx Foundation F3.1i and XSVTOOLs v3.2. It is assumed that these tools have been successfully installed. The design flow described should apply to all the VHDL designs in this collection for the FPGA. As an example, the design flow will be explained step by step for the Audio Project design.

5.1 Creating the project

1. Create a folder to contain the project description file (*.pdf file) and all the project’s associated files.

Example: The example in this section will explain the design flow for the Audio Project design. To begin with, we create a folder on C:\ called “audio”.

2. Start the Foundation Project Manager by clicking: Start / Programs / Xilinx Foundation Series 3.1i / Project Manager.

3. In the “Getting Started” dialog box, select “Create a New Project” and click OK.

4. In the “Name” field, type a name for your project. Change the “Directory” field to the folder you created in step 1. (Clicking “Browse” lets you find the folder graphically). The value for “Type” should read “F3.1i” (the same as the version of Foundation). For the “Flow” heading, select the “HDL” option. Then press OK.

Example: We will call the project “audio” to match our directory name. The completed dialog box for this example should look like the following:

Foundation will create a folder with the pathname “C:\audio\audio”. The Project Manager window should now look something like the following:

5. You now need to add the VHDL files to the project. Click on the “Project” menu and select “Add Source File(s)…”. A standard “Open” dialog box will be displayed. Select the file you wish to add to the project, then click “Open”. You can hold down the Shift or Ctrl keys to select multiple files within the dialog box.

Example: The Audio Project design consists of the following files:

· audio.vhd

· audiotop.vhd

· player.vhd

· recorder.vhd

· remap.vhd

· sram512k32bit50mhz-sv05.vhd

After saving these files to your local hard drive, add each of them to the “audio” project using the procedure described above. After doing this, the Project Manager window should look something like the following:

As each VHDL file is added to the project, Foundation will analyse the syntax of each file. It will report any errors it finds in the console section of the main window.

To edit any of the VHDL files in the project, simply double-click on the name of the file in the Project Manager window. This will open the HDL editor. When you open the editor in this way, any changes you save are automatically detected by the Project Manager.

If at some stage you make changes to a source file but the Project Manager does not detect that your file has changed, you can force it to notice the changes by telling it to re-analyse the file. To do this, right-click on the file in the Project Manager and select “Force Analysis”. To do this for every file in the project, click the “Synthesis” menu and select “Force Analysis of All Sources”.

5.2 Synthesizing the project

6. Once all the VHDL source files have been added to the project, you can synthesize the design. In order to perform synthesis for the first time, Foundation needs to know which of your VHDL entities is the top-level entity. Conversely, when you specify the top-level entity, Foundation automatically assumes that you wish to synthesize your design.

So, to specify the top-level entity and synthesize the design, click on the plus-sign next to the file containing the top-level entity. A list of the VHDL entities contained in that file is displayed. Right-click on the entity that is to be the top-level entity and select “Set as Top Level…”.

The “Create Version” dialog box is displayed.

Example: In the Audio Project design, the file “remap.vhd” contains the top-level entity, also called “remap”. Carry out the instructions above to set “remap” as the top-level entity.

7. In the “Create Version” dialog box, ensure that the target device matches the Virtex FPGA on your XSV board. The “Family” heading should read “Virtex”. The “Device” and “Speed” headings can be determined from the markings on your FPGA. Do not press “Run” nor “OK” just yet.

Example: Our FPGA has the following markings, which determine the values to be set in this dialog box:

We therefore set “Device” to “V300PQ240” and “Speed” to “-4”. The dialog box should look something like the following:

8. Foundation allows you to set some options that control synthesis. To set these click the “SET” button to the right of the “Synthesis Settings” heading. The following dialog box will be displayed:

Set any of these options that you wish to, then click OK.

Example: The Audio Project project is designed to work with a 50MHz clock signal. We specify this by entering “50” under the “Target Clock Frequency” heading. This setting does not guarantee that a particular design will work at the specified frequency, but it provides the synthesis engine with a target frequency to aim for.

We also choose to optimise for “Speed” and set the synthesis effort level to “High”. We then click OK.

To commence synthesis, click “Run” in the “Create Version” dialog box.

Foundation will synthesize the design, reporting the results in the “Console” section of the main window.

Example: If synthesis is successful, the main window should look something like the following:

Any errors that occur during synthesis will also be reported in the “Console” section of the window.

Note that Foundation attaches its own version number to every successful synthesis of a project. This version number is shown in the “Flow” section of the main window.

At this stage of the design flow, you can simulate the synthesised design by clicking on the “Simulation” button. This launches the Logic Simulator which allows you to simulate and test the design using a graphical interface.

The Implementation phase of the design flow can now be run.

5.3 Implementing the project

9. Click on the “Implementation” button in the “Flow” section of the main window. The “Synthesis/Implementation settings” dialog box is displayed, as shown below. This is identical to the “Create Version” dialog box displayed previously, but now only the options relating to Implementation are available to be modified.

Clicking the “Options” button displays the following dialog box, which allows various options for different steps of the Implementation design flow to be adjusted:

The main option you may wish to adjust is the Place & Route Effort Level. Click OK to return to the “Synthesis/Implementation settings” dialog box.

Example: For the Audio Project design, you can leave all the options at their default values. This means you don’t need to change the Place & Route Effort Level.

10. All stand-alone designs in this collection have an associated User Constraints File (UCF) that specifies which ports in the VHDL design are connected to which pins on the Virtex FPGA.

The “Synthesis/Implementation settings” dialog box should still be visible. To specify a UCF to the Implementation tools, click the “SET” button to the right of the “Control Files” heading. The following “Settings” dialog box is displayed:

11. Click the down arrow next to the “Use Constraints file from” and click “Custom”. A dialog box appears allowing you to specify the UCF. Clicking “Browse” allows you to select the UCF graphically.

Example: The UCF for the Audio Project is called “audiopins.ucf”. Specify this file in the “Custom” dialog box and click “OK”.

Click “OK” in the “Settings” dialog box.

Finally, cli