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 Verification is No Simulation

Archive for September, 2009

SystemVerilog: The finer details of $root versus $unit

Friday, September 25th, 2009

Another installment of “Longwinded Answers to Frequent SystemVerilog Questions: $unit versus $root”

Believe me – I tried to make this shorter. It’s difficult for me to explain things without a historical perspective.

Verilog was invented to be an interpreted language. Verilog-XL was (and still is) an interpretive engine with single compilation unit use model. In an interpreted engine, all of the source code is parsed and loaded into memory. This means you have to specify all the source files of a design, including the source files of any required libraries, within a single command line before simulating.

VCS (Verilog Compiled Simulator) continued this single compilation use model even though it compiled the code into a machine object saved on disk. Later, it introduced an incremental compile feature that only compiled certain files that needed it, but you still had to specify all the source files on the command line. This is not the same as separate compilation available in most software programming languages where source code can be converted into machine code independently.


SystemVerilog Coding Guidelines

Friday, September 11th, 2009

I have lots of blog entries about 95% ready to publish. This entry is from an e-mail I wrote a few months ago when somebody asked about SystemVerilog coding guidelines. I thought it would make a good article. It’s been sitting as a draft because I always have trouble finding the right title or opening words to catch people’s attention. I couldn’t come up with anything better, so here it is: SystemVerilog Coding Guidelines

My official position about this is that you pick a style and stick to it.

Which style you pick is far less important than developing the required culture that will follow it. People can spend hours arguing over the merits of camelCaps versus under_score, but once the decision is made, people on the project need to document it, adhere to it, and police it. Otherwise you’re just wasting everyone’s time.

Why are coding guidelines so important? So someone else can read your code, or maybe you can read your own code six months after you wrote it. Good comments and documentation are an import part, but you still need to be able to read the code.


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