In my last article on plain old Verilog Arrays, I discussed their very limited feature set. In comparison, SystemVerilog arrays have greatly expanded capabilities both for writing synthesizable RTL, and for writing non-synthesizable test benches. In this article, we’ll take a look at the synthesizable features of SystemVerilog Arrays we can use when writing design … Read more
The difference between Verilog reg and Verilog wire frequently confuses many programmers just starting with the language (certainly confused me!). As a beginner, I was told to follow these guidelines, which seemed to generally work: Use Verilog reg for left hand side (LHS) of signals assigned inside in always blocks Use Verilog wire for LHS … Read more
SystemVerilog struct (ure) and union are very similar to their C programming counterparts, so you may already have a good idea of how they work. But have you tried using them in your RTL design? When used effectively, they can simplify your code and save a lot of typing. Recently, I tried incorporating SystemVerilog struct … Read more
Apology for the lack of updates, but I have been on a rather long vacation to Asia and am slowly getting back into the rhythm of work and blogging. One of my first tasks after returning to work was to check over the RTL of an asynchronous FIFO in Verilog. What better way to relearn … Read more
Finite state machine (FSM) is one of the first topics taught in any digital design course, yet coding one is not as easy as first meets the eye. There are Moore and Mealy state machines, encoded and one-hot state encoding, one or two or three always block coding styles. Recently I was reviewing a coworker’s … Read more
Verilog engineers will be familiar with using Verilog always to code recurring procedures like sequential logic (if not, refer to my article Verilog Always Block for RTL Modeling), and most will have used always @(*) to code combinational logic. SystemVerilog defines four forms of always procedures: always, always_comb, always_ff, always_latch. What do the three new … Read more
Improperly coded Verilog case statements can frequently cause unintended synthesis optimizations or unintended latches. These problems, if not caught in pre-silicon simulations or gate level simulations, can easily lead to a non-functional chip. The new SystemVerilog unique and priority keywords are designed to address these coding traps. In this article, we will take a closer … Read more
In part 2 of this series, SystemVerilog and Verilog X Optimism – What About X Pessimism?, I discussed several coding styles that help to reduce the risk of missing design bugs due to Verilog X optimism. In part 3, we will take a look at how proprietary simulator features help avoid the problem by smartly … Read more
In my previous post about SystemVerilog and Verilog X Optimism – You May Not Be Simulating What You Think, I discussed what is Verilog X optimism, and some coding styles that are prone to Verilog X optimism bugs. So how do you avoid potential bugs that Verilog X optimism can introduce? One technique that has … Read more
Verilog and SystemVerilog define 4 different logic values for modeling hardware: 1, 0, X, and Z. 1 and 0 are obviously real logic levels that can exist in silicon. Z and X, however, are modeling abstractions: Z represents a high-impedance (an un-driven or tri-stated signal) state, while X represents an unknown or indeterminate logic value. X’s … Read more