Engg Technical notes

1. Why Learn Compiler Directives? Before we even write a line of HDL, let’s answer a simple question: “When the Verilog compiler reads your code, how does it know what to include, what to skip, what constants to use, and how to interpret time?” The answer lies in compiler directives — special preprocessor instructions that guide the compiler before actual synthesis or simulation begins. They don’t create flip‑flops, gates, or signals; instead, they control the environment in which your design is understood and simulated. Think of it this way: Your Verilog compiler is like a translator. Directives are the translator’s instructions : “Before you translate, read this extra file,” “Replace this word everywhere,” “If the designer says debug is on, include extra print statements,” etc. Without these, large designs become unmanageable — hundreds of modules, testbenches, and configurations would be impossible to maintain. 2. The Preprocessor: What Happens Before Compil...

Chapter 1: Introduction to Assertions 1.1 What are Assertions? Definition : Assertions are statements in HDL that check if a design behaves as expected during simulation. They do not change the design behavior , but monitor it. Think of them as automatic examiners : they raise an alert if something goes wrong. Example Analogy: Imagine a traffic light controller. Assertion: “The red and green lights should never be ON at the same time.” If violated, simulation stops or logs a warning. 1.2 Assertion Languages SystemVerilog Assertions (SVA) – built-in assertions in SystemVerilog Open Verification Library (OVL) – a library of reusable assertion modules Property Specification Language (PSL) – industry-standard assertion language 1.3 Advantages of Using Assertions Early Detection of Bugs: Catches design violations during simulation. Self-Checking Testbenches: Reduces manual verification effort. Reusable Verification Components: Assertion...

     When we design digital circuits in Verilog , we often rely on primitives —the building blocks of complex systems. These are the lowest-level components (gates, switches, buffers, etc.) that mimic real hardware behavior. Understanding how to design using primitives is crucial, especially in ASIC (Application-Specific Integrated Circuit) and library development . In this blog, we’ll cover: ✅ What Verilog primitives are ✅ How delays are modeled (rise, fall, turn-off, min/typ/max) ✅ Examples of gate delays with testbenches ✅ N-input and N-output primitives ✅ Building complex circuits (AND gate, D-Flip-Flop, Multiplexer) using primitives Let’s dive in 🚀 🔹 What are Verilog Primitives? Primitives are the basic logic gates and switches provided by Verilog. They are built-in keywords like and , or , not , buf , etc. They do not require module definitions (unlike user-defined modules). ASIC vendors often use User-Defined Primitives (UDP) and standard gate...

When we think of Verilog , most engineers picture RTL (Register Transfer Level) coding – writing always blocks, designing with if-else or case statements, and abstracting digital logic into behavioral or dataflow descriptions. However, Verilog also provides a lower-level way of modeling hardware, called Gate-Level Modeling . This is where you describe your circuits directly in terms of logic gates , switches , and transistor-level primitives . Even though gate-level coding is rarely used in RTL design , it plays a vital role after synthesis in ASIC and FPGA design flows . Let’s break it down. 🔑 Why Gate-Level Modeling Matters RTL Coding → Synthesis → Gate-Level Netlist In real chip design, RTL code is synthesized into logic gates . The synthesis tool generates a Verilog netlist made of gate primitives and standard cells . Gate-Level Simulation (GLS) This netlist is then simulated (often with back-annotated timing from an SDF file ) to check how the design behaves w...