Clock tree synthesis implementing the clock trees 770 ic compiler implementation user guide d2010. Switching activity is high, since clock toggles constantly. This process results in a timing optimization design with fully implemented clock trees. Ese566a modern systemonchip design, spring 2017 3 figure 4. Dec 18, 2012 clock tree begins at sdc synopsys design constraints defined clock source. It utilizes the galaxy design platform physical implementation technologies to derive accurate interconnect delay data that allows the design compiler solution to predict postlayout design results such as. Clock tree networks are pillars and columns of a chip. The relation of synchronization to the design of the clock distribution network is presented in section 5. Hi i was wondering if anyone has ideas on how to synthesize a htree clock network using synopsys design compiler i have some ptm models for 32nm nmos and pmos. Using synopsys design compiler and primetime is intended for anyone who is involved in the asic design methodology, starting from rtl synthesis to final tapeout. Design compiler topographical technology is an innovative, tapeoutproven synthesis technology that significantly reduces design time. What are the timing constraints in design compiler that can cause problems in the backend, clock tree synthesis, and propagated clocks. Think of it as a timing window that stretches according to the clock arrival time at launch flop and arrival at destination flop.
Type commands to the design compiler shell start with syndc and start typing 2. The goal of clock tree synthesis cts is to minimize skew and insertion delay. Wakeup scheduling and its buffered tree synthesis for. Cic training manual logic synthesis with design compiler, july, 2006 tsmc 0 18um process 1 8volt sagextm stand cell library databook september 2003 t. In most of the ics clock consumes 3040 % of total power. Clock power consumption depends on switching activity and wire length. Power clock is a major power consumer in your design.
Clock tree synthesis originally posted by seahwan95. Oct 16, 2017 clock tree synthesis cts is one of the most important stages in pnr. Jsbgm islped08 clock network power clock network power consists of clock tree buffer power clock tree dynamic power due to wires clkq sequential internal power leaflevels drive the highest capacitance in the tree 80% of the clock network dynamic power is consumed by the leaf driver stage. Power aware clock tree synthesis part 2 vlsi system design. A free powerpoint ppt presentation displayed as a flash slide show on id. To see the clock tree exceptions defined in your design, generate a clock tree exceptions report. In addition, crucial issues related to layout, which includes clock tree synthesis and backend integration links to layout are also discussed at length. This accurate interconnect delay data allows the design compiler tool to predict postlayout design results such as timing, testability and area during synthesis.
Synopsys design compiler topographical technology accelerates. Clock is not propagated before cts as shown in the picture. Addressing clock tree synthesis challenges design and reuse. Automated synthesis from hdl models auburn university. Cluster clock nodes and build a local tree by the load balance based cts methods create a buffered rc network from the local clock tree minimize clock skew by wire sizing and snake routing zadvantages. An efficient clock tree synthesis method in physical design. Ic compiler ii is specifically architected to address aggressive performance, power. Ic compiler ii includes innovative for flat and hierarchical design planning, early design exploration, congestion aware placement and optimization, clock tree.
A variationadaptive design flow that uses adjustable delay buffers adb in wakeup network to satisfy i max. Synthesis of dualmode circuits through library design, gate. Clock tree synthesis clock tree synthesis cts is the process of inserting buffersinverters along the clock paths of the asic design to balance the clock delay to all clock inputs. To specify clock tree exceptions for the current scenario. Cic training manual logic synthesis with design compiler, july, 2006.
Clock distribution and balancing methodology for large and. Ic compiler ii includes innovative for flat and hierarchical design planning, early design exploration, congestion aware placement and optimization, clock tree synthesis, advanced node routing convergence, manufacturing compliance, and signoff closure. Lets take the excitement to next post, where i will solve the above problem and also design a clock network, with above solutions. Tutorial for encounter washington university in st. This paper proposes a method aiding in low clock skew applicable to the mainstream industry clock tree synthesis cts design flow. Wakeup scheduling and its buffered tree synthesis for power. Specifying clock tree synthesis goals the optimization goals used for synthesizing the design and the optimization goals used for synthesizing the clock trees might differ. In reality, after the cts, there are small differences between clock arrival time at the nodes of the tree. The clock skew scheduling problem for more popular register type of edgetriggered flipflops is described in section 5. What is clock uncertainty, clock skew and clock jitter.
I would like to synthesize a 3 level h tree to analyze the clock skew and temperature variance. The goal of cts is to minimize the skew and latency. Some useful definitions and notations are introduced in section 5. Ese566a modern systemonchip design, spring 2017 ese. Before implementing the clock trees, save the design. Clock tree begins at sdc synopsys design constraints defined clock source. Sep 30, 2016 clock tree synthesis clock tree synthesis is a process which makes sure that the clock gets distributed evenly to all sequential elements in a design. Clock tree buffer power clock tree dynamic power due to wires clkq sequential internal power leaflevels drive the highest capacitance in the tree 80% of the clock network dynamic power is consumed by the leaf driver stage. As mentioned above clock will also be given to input pin of combinational block but very rarely in low power techniques such as clock gating etc. Clock tree synthesis is a longstanding technique widely available in place and route tools whereby the tool is tasked with automatically matching the arrival time of the clock signal at each target in the clock network by building a tree of buffers and inverters distributed across the design.
Use the design vision gui friendly menus and graphics. What are the timing related commands with respect to clock. In addition, the entire asic design flow methodology targeted for vdsm verydeepsubmicron technologies is covered in detail. From this dc result, is it possible to generate a spice netlist for. Dont touch circuits and pins in front end logic synthesis are treated as ignore circuits or pins at back end physical synthesis. Defines the clock tree exceptions for all master clocks that contain the paths of the pin, including the paths of the generated clocks. I would like to use cmos inverter as a buffer at each branchleaf. Power aware clock tree synthesis part 2 hello while trying to build a clock tree which is power aware, lets go back a step ahead and look, what are the top observations for a clock network, and below image covers the same. Synopsys design compiler topographical technology expedites. Advanced asic chip synthesis download ebook pdf, epub. This is motivated by the fact that the proportion of loaddependent.
Tseng, ares lab 2008 summer training course of design compiler. Sometimes the difference helps you, sometimes it hurts you. Hi i was wondering if anyone has ideas on how to synthesize a h tree clock network using synopsys design compiler i have some ptm models for 32nm nmos and pmos. Static timing analysis sta interview questions static timing analysis interview questions static timing analysis plays major role in physical design pd flow. Synopsys design compiler generate gatelevel netlist. Static timing analysis sta interview questions static timing analysis interview questions static timing analysis plays major role in physical designpd flow.
This allows you to refine the clock tree synthesis goals and rerun clock tree synthesis with the same starting point, if necessary. Clock tree synthesis is a process which makes sure that the clock gets distributed evenly to all sequential elements in a design. This paper aims to share practical experience regarding building a poweroptimized clock tree, determining the optimum targets for clock tree synthesis cts and monitoring the quality of results qor along the way. Clock gating for power optimization in asic design cycle. Mar 21, 2015 47 as always, it is a good idea to experiment and try out different cts options and intparams to get the best result. Jan 10, 2014 clock tree synthesis is a process which makes sure that the clock gets distributed evenly to all sequential elements in a design. The original clock root is partitioned into several pseudo clock. In addition, the entire asic design flow methodology targeted for vdsm verydeepsubmicron. Clock tree synthesis cts plays an important role in building wellbalanced clock tree, fixing timing violations and reducing the extra unnecessary pessimism in the design. Integration of wakeup scheduling and buffered tree synthesis into a complete design flow, which receives a netlist of a power gated circuit and produces a layout where wakeup network is embedded. At the end of the workshop, you will have a design that can be passed on to clock tree synthesis and routing. In front end, you set ideal network conditions on certain pinsclocks etc. We will discuss about skew and insertion delay in upcoming posts. Design compiler synthesis of behavioral to structural three ways to go.
Clock tree synthesis clock tree synthesis is a process which makes sure that the clock gets distributed evenly to all sequential elements in a design. It includes flat and hierarchical design planning, placement, clock tree synthesis, routing and optimization, manufacturability, and lowpower capabilities that. While trying to build a clock tree which is power aware, lets go back a step ahead and look, what are the top observations for a clock network, and below image covers the same assuming a slew of 40ps for the first buffer and capacitance of 60ff on node a, the delay of the first buffer can be easily evaluated using below nldm table and it comes out to be x9. Since we usually let the clock tree synthesis cts procedure. So in order to balance the skew and minimize insertion delay cts is performed. The goal during building a clock tree is to reduce the skew, maintain symmetrical clock tree structure and to cover all the registers in the design. I would like to synthesize a 3 level htree to analyze the clock skew and temperature variance. Source codes and calibration scripts for clock tree synthesis theopenroad projecttritoncts.
Advanced asic chip synthesis using synopsys design. In addition, the topographical attribute utilizes clocktree synthesis technology to estimate a designs postlayout power consumption. Using synopsys design compiler physical compiler and primetime, second edition describes the advanced concepts and techniques used towards asic chip synthesis, physical synthesis, formal verification and static timing analysis, using the synopsys suite of tools. Learn to use fusion compiler to perform complete physical synthesis, which is the unification of traditional synthesis and iccii placement functionality. This site is like a library, use search box in the widget to get ebook that you want. Clock tree synthesis clock tree synthesis cts is the process of inserting buffersinverters along the clock paths of the asic design to. Furthermore, the book contains indepth discussions on the basis of synopsys technology libraries and hdl coding styles, targeted towards optimal synthesis solution. The placement data will be given as input for cts, along with the clock tree constraints. Note before implementing the clock trees save your design.
High fanout net synthesis hfns vlsi basics and interview. Oct 11, 2007 what is clock uncertainty, clock skew and clock jitter. Advanced asic chip synthesis using synopsys design compiler. There are two types of stop pins known as ignore pins and sync pins. We have captured some problematic scenarios and the problem solving. Clock tree synthesis cts cts quality checks skew, power, latency, etc. Clock tree ends at clock pins of ff or hard macros or input pins of combinational logic also. Click download or read online button to get advanced asic chip synthesis book now. In addition, the topographical attribute utilizes clock tree synthesis technology to estimate a design s postlayout power consumption. Power aware clock tree synthesis part 3 vlsi system design.
The goal of clock tree synthesis is to get the skew in the design to be close to zero. Before implementing the clock trees, save your design. Clock tree synthesis cts is one of the most important stages in pnr. Ppt fpga design flow powerpoint presentation free to. Htree quality check of htree clock tree buffering buffered htree htree with uneven spread of flops advanced htree for million flops power aware cts clock gating static timing analysis with. Clocktree synthesis is reformulated to minimize clock skew at both modes. And heres the solution to the problem posted in my previous article. Ic compiler also considers the design rule constraint values from the logic library and the design. In addition, topographical technology utilizes clock tree synthesis technology to estimate postlayout power results of the design, resulting in a highly predictable.
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