Greg Stitt

Portable RAM Inference Templates for FPGAs

RAMs are a fundamental part of most digital designs, yet there’s still no widely adopted RTL template for inferring RAMs that works reliably across all FPGAs. As a result, many designers resort to manually instantiating RAM primitives or using vendor-specific IP cores. While this approach gets the job done, it’s often tedious and undermines portability—one […]

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Is Retiming a Productivity Shortcut?

Retiming is a powerful optimization used in synthesis and digital-circuit design to improve the maximum clock frequency. Retiming works by relocating registers from paths with sufficient slack into paths with timing violations, essentially sacrificing slack from some paths to improve the timing of others—a strategy often referred to as “stealing slack.” For example: In this

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Race Conditions: The Root of All Verilog Evil

If you’ve worked with Verilog or SystemVerilog, you’ve likely encountered the term race condition—and, if you’re like most engineers, you may not fully understand why they happen or how to avoid them. If that’s the case, don’t worry; you’re certainly not alone. Even seasoned experts with decades of experience, myself included, occasionally run into race

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Recognizing the Signs: My Journey Through an Unlikely Heart Attack

I never planned to write a non-technical article on this site, but I also never imagined having a heart attack while in seemingly excellent health. Given how closely timely medical intervention is tied to the outcome, I consider myself incredibly fortunate to have been in surgery within an hour of the event. In this article,

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Optimizing Hardware For FPGAs

If you’ve studied digital design, you have likely used a field-programmable gate array (FPGA) to implement custom circuits. This widespread use of FPGAs stems from their flexible and reconfigurable architecture, which can support potentially any register-transfer level (RTL) design. However, unless you have deployed a highly constrained FPGA application, you might not have considered how

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RTL Code is Weird: Part 1

Register-transfer-level (RTL) development is widely known to be considerably more difficult than developing with more common high-level languages. The primary reason for this increased difficulty lies in the necessity for hardware expertise to craft efficient designs. However, even seasoned hardware engineers encounter distinct challenges that diverge sharply from those encountered in software development. These challenges

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RTL Pitfalls: Stop Initializing Signals, Start Testing Resets, and Use Assertions

In this article, we again explore the intricacies of register-transfer-level (RTL) coding, investigating several often-overlooked topics that frequently lead to pitfalls in design. We then discuss more general verification techniques that help identify these pitfalls, and others as soon as possible. To help connect these topics, we use the following example, which has a subtle,

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You Can (and Should) Write Recursive RTL: Part 2

After the positive reception of my initial post on recursive RTL, which sparked numerous insightful discussions, I’m excited to present Part 2. In this installment, I’ll delve into addressing common misunderstandings while also introducing an optimization technique for the adder tree discussed previously. Why not create an adder tree through iterative accumulation? This question emerged

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