There is a crucial step between Coarse Placement and Legalization, known as Scan Reorder, which involves the processing of the Scan Chain. The term "Scan Reorder" literally translates to "scan chain reorganization." This stage plays an essential role in optimizing the layout of scan chains, improving testability, and reducing routing congestion. Before diving into Scan Reorder, it's important to understand what a Scan Chain is. A Scan Chain is a fundamental concept in Design for Testability (DFT), a methodology used to make digital circuits more testable by enabling internal signals to be controlled and observed from outside the chip. Since the internal structure of a chip is typically a "black box," DFT allows testers to access and manipulate the state of internal flip-flops through dedicated scan paths. Scan Chains are implemented by replacing standard flip-flops with scan flip-flops (SFFs) that can be configured in either normal mode or scan mode using a control signal called Scan Enable (SE). In normal mode, SFFs behave like regular flip-flops, while in scan mode, they act as shift registers, allowing test patterns to be shifted in and out. The structure of a scan cell includes three ports: SI (scan input), SO (scan output), and SE (scan enable). These ports allow the scan chain to be connected end-to-end, forming a path through which test data can be loaded and captured. In backend physical design, the Scan Chain is a key element. It enables efficient testing of the chip by providing a way to observe and control internal states. Once the scan chain is inserted, the design tools automatically replace standard flip-flops with scan flip-flops and connect them in a serial chain. The definition of scan chains is often specified in a DEF file, referred to as a "scan def." This file contains information about the order and connections of scan cells, including floating and ordered units. For example, a scan chain might start at a specific pin, include several floating flip-flops, and then connect to ordered elements such as buffers or other logic components before ending at a scan output pin. After coarse placement, scan cells are often placed randomly, leading to long and inefficient routing. This is where Scan Reorder comes into play. By rearranging the order of scan cells without affecting the logic function, Scan Reorder reduces the length of interconnections, making the layout more compact and efficient. Visual examples show the difference before and after Scan Reorder. Before the process, the scan chain connections appear messy and disconnected, often referred to as "detour" routing. After reordering, the connections become more linear and structured, significantly reducing the number of traces and improving overall routability. In terms of the DEF file, the scan chain definition changes to reflect the new order. A marker such as "#" is used to indicate the position of reordered elements within the chain, ensuring proper alignment and connectivity. Finally, tools like `report_scan_chains` and `check_scan_chain` are used to verify the correctness and efficiency of the scan chain configuration. These commands help ensure that all scan segments are valid, have the correct length, and are properly partitioned across different regions of the chip. By carefully managing the scan chain during the physical design flow, designers can enhance testability, reduce area, and improve performance—all critical factors in modern chip design.

Photovoltaic Dual-Axis Tracking Bracket

Photovoltaic Dual-Axis Tracking Bracket,Completed Double axis System,Double axis System application,components of Dual Axis Solar Trackers

Hebei Shuobiao New Energy Technology Co., Ltd. , https://www.pvbracketsystem.com