An Editor for HDLs

• HDLs
• Tips and Tricks
• HowTos

Unless you're still living in the '90s and using schematics, your FPGA designs are entered into text files as VHDL or Verilog source. Which, of course, implies you're using some form of text editor. Now, right after brace placement in C, the choice of an editor is the topic most likely to incite a nerd civil war (it's a bike-shed issue). I won't attempt to influence your choice because it really makes no difference to me. But if you are using the same editor I do, then maybe I can help you use it more efficiently.

A poll on HDL editor popularity shows that Emacs is the winner by a wide margin with a 31% share, while vim and Notepad++ are tied at around 15% each. The remaining 39% is split between a hodge-podge of generic and IDE-specific text editors (e.g., the Xilinx ISE and Altera Quartus editors).

Emacs is most popular for good reason. It has powerful add-on packages that make creating and refactoring source code much easier. This includes packages for working with VHDL and Verilog code. It's also been widely ported, so you can use Emacs on just about any OS you'll encounter.

That said, I don't use Emacs. I had my love affair with it in the '90s but it just didn't work out. There were so many keystroke combinations involved in using it that I felt like I was casting strange incantations instead of entering code.

Over a period of years, I drifted through several Windows-specific editors like Zeus and Programmers File Editor. But I finally settled on Notepad++ as my editor of choice. Right out of the box it has:

• VHDL and Verilog syntax highlighting.
• Code folding.
• Block selection and column editing.
• Auto indenting.
• Configurable hot keys.

That's good, but it could be better. For VHDL and Verilog, I specifically needed templates, automated package declarations, and code beautification. Here's how I got those.

HDL Templates

If you're like me and you do a lot of things in addition to HDL coding, it can be frustrating trying to get all the syntax correct when you enter a new HDL module after being away from it for a while. Having a set of predefined templates for things like entities, functions, processes, etc. provides a strong code skeleton that I can flesh out with the appropriate I/O and signal declarations. Templates also help keep me consistent with the accepted HDL coding style. And filling-in a template is faster than recreating the code each time.

Notepad++ has a long list of plug-ins that extend its features. Several of these plug-ins, FingerText, NppSnippets and SnippetPlus, allow me to name and store blocks of code as snippets that I can later add to new source files with just a few key strokes or mouse clicks.

I chose FingerText because its macro language seems more powerful and flexible. Just typing module and a TAB into a file produces a VHDL entity and architecture with hotspots that the cursor will jump to so I can fill-in the entity name, inputs and outputs. Here is some additional information on using FingerText and a link to my set of VHDL snippets. You can modify and extend these snippets to match your own coding style, or create a new set for Verilog.

Automated Package Declarations

I always like to place a package body at the top of each VHDL file that contains the component declarations for any entities I've defined further down in the file. That makes it easy for me to instantiate these components in other VHDL source files without having to enter the component declaration in multiple places.

However, it's a pain to keep the component declarations in the package sync'ed with their associated entities as the input and output names are changed during development. So I developed a simple Perl script that manages this task for me and linked it to a Notepad++ hotkey. For example, if I enter a few entity-architecture pairs like these:

Then when I hit the hotkey, the following package is generated at the top of the file:

(Naturally, I change the initial NewPckg name to something more meaningful after the script runs.)

perl C:\bin\vhdlpckg.pl $(FULL_CURRENT_PATH)

C:\bin\emacs-24.1\bin\emacs.exe -batch $(FULL_CURRENT_PATH) -f vhdl-beautify-buffer -f save-buffer

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