VHDL: Xilinx ISE

VHDL Tutorial A brief guide to VHDL design with a design example; the introduction and core of the tutorial. < prev next >

Now that we've discussed VHDL itself, it's time to learn the development environment. If you don't already have it installed, you will want to install the Xilinx ISE WebPACK. The ISE Foundation is a professional tool that will cost you an arm and a leg. The ISE WebPACK is a free version of the software that does most of what you need (unless you have large, complex designs or are working with the newest and best Xilinx FPGAs). If you know ahead of time which series of FPGAs you plan to use, you can save time and disk space by only installing the files for that FPGA series. Once you've got that installed, fire it up.

Creating a new project

Go to File > New Project to start the New Project Wizard. Give your project a name. Something not too long that will help you find the files later. Then give the program a location to put the project; ISE will create a subfolder in that directory with the name of your project. And finally, your top-level source type is HDL (Hardware Description Language).

The next dialog box asks a whole lot of questions. But worry not; we'll keep it fairly simple. Choose your device family; for our project that will be the Spartan-3A (on the pull-down menu you'll find "Spartan3A and Spartan3AN"). The device is unknown for our project. We plan to design the VHDL first, then find out how large of an FPGA we need to hold our design. So just go ahead and pick the smallest Spartan-3A: XC3S50A. If need be we'll adjust the project later to use a larger FPGA. If you know the package, go ahead and select that. However, once again, we'll probably figure that out later, so I just left the default. Skimming down past several options you can leave alone (unless you know you're using something other than the defaults), make sure your simulator is set to "ISE Simulator (VHDL/Verilog) and your preferred language is VHDL. Then go ahead and hit next.

If you want to create a brand-new file right up front, go ahead. However, I will explain creating new files a bit later, so you can just skip this step and add the files later. Click next. If you have existing source files from somewhere else that you want to include, this is the place for you. Chances are you're starting from scratch, so you can just click next. Then you get a summary box to make sure you got everything right. If so, click Finish.