11/8/2022 0 Comments Fifo verilog code basic![]() Worse yet, that next flip-flop may also go metastable, causing metastability to propagate through the design! Synchronizers for Clock Domain Crossing (CDC)Ī synchronizer is a circuit whose purpose is to minimize the probability of a synchronization failure. Synchronization failure occurs when the output of the destination flip-flop goes metastable and does not converge to a legal state by the time its output must be sampled again (by the next flip-flop in the destination domain). In an asynchronous clock domain crossing (CDC), where the source and destination clocks have no frequency relationship, a signal from the source domain has a non-zero probability of changing within the setup or hold time of a destination flip-flop it drives. One of the ways a flip-flop can enter a metastable state is if its setup or hold time is violated. When applied to flip-flops in digital circuits, it means a state where the flip-flop’s output may not have settled to the final expected value. In layman’s terms, metastability refers to an unstable intermediate state, where the slightest disturbance will cause a resolution to a stable state. Let’s get right to it! What is Metastability?Īny discussion of clock domain crossing (CDC) should start with a basic understanding of metastability and synchronization. Part 3 – design of a complete multi-bit synchronizer with feedback acknowledge.Part 2 – challenges with passing multi-bit signals across a CDC, and multi-bit synchronizer.Part 1 – metastability and challenges with passing single bit signals across a clock domain crossing (CDC), and single-bit synchronizer. #FIFO VERILOG CODE BASIC VERIFICATION#The concepts in this article are mostly taken from Cliff Cumming's very comprehensive paper Clock Domain Crossing (CDC) Design & Verification Techniques Using SystemVerilog. This is perfect timing because I’m just about to create a new revision of one of my design blocks at work, which incorporates many of these concepts. ![]() Thank you for all your interest in my last post on Dual-Clock Asynchronous FIFO in SystemVerilog! I decided to continue the theme of clock domain crossing (CDC) design techniques, and look at several other methods for passing control signals and data between asynchronous clock domains. ![]()
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