Understanding $Rose and $Fell in SystemVerilog | Edge Detection Explained

Why It Matters

Accurate edge detection is critical for writing correct assertions and synchronous logic in SystemVerilog; understanding $rose/$fell and their sampling semantics prevents missed or spurious events in verification and design. Confusion around transitions at the clock edge can lead to subtle bugs in timing checks and assertions.

Summary

The video explains SystemVerilog's $rose and $fell system functions (referred to as “dollar rows” and “dollar fill” in the transcript) for edge detection. $rose returns true on a 0→1 transition of a signal at the sampled clock edge, while $fell returns true on a 1→0 transition; otherwise they return false. The presenter walks through timing waveforms to show how these functions sample the stable value just before a clock edge and highlights behavior when transitions occur at the edge. Several examples illustrate when each function produces a pulse or remains zero.

Original Description

In this video, we will learn about $rose and $fell in SystemVerilog and understand how these functions are used for edge detection in assertions and verification environments.

Topics Covered:

What is $rose in SystemVerilog?

What is $fell in SystemVerilog?

Rising edge detection

Falling edge detection

Syntax and working

Examples using SystemVerilog Assertions (SVA)

Difference between $rose and $fell

Usage in verification and protocol checking

This video is useful for:

VLSI Engineers

FPGA Engineers

Verification Engineers

Students learning SystemVerilog & UVM

Watch till the end to clearly understand edge detection concepts in SystemVerilog Assertions.

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Verilog, SystemVerilog, UVM, Assertions, FPGA, RTL Design, and VLSI Verification.

Hashtags

#SystemVerilog #SVA #Verification #UVM #VLSI #FPGA #ASIC #RTLDesign #Assertions #DigitalDesign #Semiconductor #ChipDesign #Electronics #HardwareDesign #Verilog #SystemVerilogAssertions #FunctionalVerification #VLSIEngineer #EdgeDetection #rose #fell #QuestaSim #EDA #Coding #DesignVerification #LearnVLSI #RTL #Simulation #TechEducation #AllAboutVLSI