Fusion compiler s integrated cockpit figure 1 provides a comprehensive platform for design including rtl physical synthesis, design planning, placement, clock tree synthesis cts, advanced routing, physical synthesis based optimization, chip. In future, this task will done automatically by our compiler. Clock tree synthesis cts cts quality checks skew, power, latency, etc. Introduction to clock tree synthesis career in physical. Aug 07, 20 the goal of clock tree synthesis is to get the skew in the design to be close to zero. Ese566a modern systemonchip design, spring 2017 ese 566a. Switching activity is high, since clock toggles constantly. An optimized clock tree helps to avoid serious design issues such as excessive power consumption, high routing congestion, elongated timing closure, etc 3.
Synthesis and scripting techniques for designing multiasynchronous clock designs clifford e. Use the design vision gui friendly menus and graphics. 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. During the synthesis process, all the constraints are applied to ensure the design meets the functionality and speed. Addressing clock tree synthesis cts challenges in soc. Clock power consumption depends on switching activity and wire length. Furthermore, manual refinement is done using crude estimates that can only. The buffer insertion is done more than to reduce just the skew.
An optimized clock tree helps to avoid serious design issues such as excessive power consumption, high. The goal of clock tree synthesis cts is to minimize skew and insertion delay. This is a process that is automated by an eda tool during the clock tree. Synthesis in the design flow circuit simulator router designer tasks tools text editor c compiler logic simulation synthesis cell libraries rtl simulator synthesis tools timing analyzer power estimator schematic editor. Clock tree synthesis cts up until this point, the clock tree has been treated as idealthe clock arrives to every ipop at exactly the same time. Design compiler synthesis of behavioral to structural three ways to go.
Once the timing and functionality is verified, it is sent for physical design flow. Power analysis of clock gating at rtl design and reuse. A renewed emphasis on highfrequency clock design has heightened interest in multisource clock tree synthesis cts. The clock tree synthesis functionality of the synopsys ic compiler tool has been explored. What are the good books for learning clock tree synthesis. We do not claim that our optimal gh tree is a globally optimal clock tree solution. Clock tree synthesis cts is a critical stage of physical design, since clock network often constitutes a high percentage of the overall power in the. Tseng, ares lab 2008 summer training course of design compiler tsmc 0. Fast, convergent clock synthesis and optimization with ic compiler ii growing challenges from capacity, variability and complexity need to be managed, so it is necessary to rethink both the algorithmic and infrastructural aspects of clock implementation. Optimal generalized htree topology and buffering for high.
Power clock is a major power consumer in your design. Difference between clock buffer and normal bufferinputs of clock tr. This paper will detail some of the hardware design, timing analysis, synthesis and simulation methodologies to address multi clock designs. After placement cts creates or synthesizes a buffered and balanced clock tree network. Network synthesis, clock tree synthesis, place and route and chip finishing. This transition happens at the clock tree synthesis cts step in the flow where clocks are physically built and inserted into a design see.
Reconfigurable clock trees for multicorner multimode designs. There are two books which are really good to learn about cts vlsi physical design. In addition to increasing power due to new enables, every time a clock gate is added to the clock tree it introduces an additional delay and makes clock tree synthesis more difficult. The student needs to know basic digital design and power analysis in digital logic. Use multiple drivers to distribute driver requirements. If chip design begins in a world where clocks are ideal but ends in a world where clocks are propagated, it follows that at some point in the design flow a transition must be made between these two worlds. In addition, the entire asic design flow methodology targeted for vdsm verydeepsubmicron technologies is covered in detail. If physical location wasnt a problem, clock tree synthesis would only. Clock tree synthesis part 1 digital design analog design. In the real asic design world, there are very few single clock designs.
Nov 02, 2015 design compiler dc vs ic compiler icc dc is a synthesis tool that convert rtl code into gatelevel netlist and optimize it. 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. With this command, we have created a clock on the port clk ci of our registeredadd design. Cic training manual logic synthesis with design compiler, july, 2006. In addition, the entire asic design flow methodology targeted for vdsm verydeepsubmicron. Pdf an efficient clock tree synthesis method in physical. Clock tree generation is coming under increased scrutiny because of its role in dynamic power consumption and problems caused by onchip pvt variation. The result is a postlayout netlist and a gds ii file. Basically you play with logic delay and clock skew to achieve better timing.
It reads in synthesizable verilog or vhdl files and generates a celllevel netlist according to a standard cell library. These gates could introduce clock skew and lead to setup and holdtime violations even when mapped into the soc, however, this is compensated for by the clock tree synthesis and layout tools at various stages of the soc backend flow. An optimized clock tree helps to avoid serious design issues such as exces sive power consumption, high routing congestion, elongated timing closure, etc 3. Clock tree synthesis clockpad and output need to defined in a specification file. A look under the hood of ic compiler ii, synopsys nextgeneration. In addition, crucial issues related to layout, which includes clock tree synthesis and backend integration links to layout are also discussed at length. Cic training manual logic synthesis with design compiler, july, 2006 tsmc 0 18um process 1 8volt sagextm stand cell library databook september 2003 t. From graph partitioning to timing closure handbook of algorithms for physical design automation. Design compiler introduction we use synopsys design compiler dc to. Type commands to the design compiler shell start with syndc and start typing 2. Characterization, clock tree synthesis and power grid.
For example, if the clock enable is always high, inserting a clock gate and additional enable logic will consume more power. Finally,example dc scripts were included to guide the users to perform. This tutorial covers how to implement a multisource cts design. In a manual system, the clock gates are controlled. During cts, the tool isolates exclude pins from the clock tree by inserting a guide buffer before the pin. Exclude pin are clock tree endpoints that are excluded from clock tree timing calculation and optimization.
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. This paper is not intended to provide exhaustive coverage of this topic, but is presented to share techniques. You can see that the init design icc target executes ic compiler with the following com mand. If you dont know how to use design compiler, look at. Research on clock tree synthesis and basic metrics regarding cts. Advanced h tree for million flop clock endpoints with uneven spread section 8 power aware clock tree synthesis lecture 34. A separate section was dedicated to issues related to clocks. In this paper, we propose a new clock tree synthesis method for semisynchronous circuits. In fact, there is now a single inverter driving hundreds of gates and in a bigger design, thousands. Robust chiplevel clock tree synthesis for soc designs.
Fast, convergent clock synthesis and optimization with ic. Creates the project directory tree for automated chip synthesis. Rtltogates synthesis using synopsys design compiler. Lab 4 lab 48 clock tree synthesis synopsys ic compiler 1 workshop note. H tree quality check of h tree clock tree buffering buffered h tree h tree with uneven spread of flops advanced h tree for million flops power aware cts clock gating static timing analysis with. This second edition of this book describes the advanced concepts and. A practical clock tree synthesis for semisynchronous circuits. In addition, crucial issues related to layout, which includes clock tree synthesis and backend integration links to layout a. Regional clock tree generation by abutment in synchoros. Cadence rtl compilerbuild gatesphysically knowledgeable synthesis pks. Cs6710 tool suite design compiler design compiler basic flow.
Clock tree synthesis in asic backend design atlantis press. Abstract designing a pure, one clock synchronous design is a luxury that few asic designers will ever know. Clock trees are a large source of dynamic power because they switch at the maximum rate and typically have larger. For this lab, we will continue the physical design flow by performing clock tree synthesis cts. Learnin28days is an online vlsi learning platform for beginners who are passionate to build career in semiconductor industry. This section described various techniques useful for specifying clocks,both for pre and postlayout. The tool considers exclude pins only in calculation and optimizations for design rule constraints. After placement cts creates or synthesizes a buffered and balanced clock tree. The verilog gatelevel netlist generated by synopsys dc has no physical information. Introduction to clock tree synthesis career in physical design. Clock tree synthesis for timing convergence and timing. The original clock root is partitioned into several pseudo clock. This section also included a topic on specification of generated clocks that are present in almost all designs. The integration of these techniques offers the maximum bene.
Furthermore, the book contains indepth discussions on the basics of synopsys technology libraries and hdl coding styles, targeted towards optimal synthesis solutions. Exposure to design compiler, ic compiler, z route, timing using ptptsi, physical verification drc,lvs. This dissertation provides a comprehensive study on four clock design techniques. There are two types of stop pins known as ignore pins and sync pins. Deepak dasalukunte, eit, lth, digital ic project and verification place and route clock skew absolute skewdelay from input to leaf cell relative skew. Most of the asics that are ever designed are driven by multiple asynchronous clocks and. A short introduction to synopsys ic compiler ii tech design forum. Using synopsys ic compiler the design is, first, placed, followed by the clock tree synthesis cts and, finally the routing of every cell. Clocktree synthesis for lowemi design davide pandini. In this tutorial, we are going to run design compiler in a scriptbased flow, so most work will be done automatically. Clock gating for power optimization in asic design cycle. This paper proposes a method aiding in low clock skew applicable to the mainstream industry clock tree synthesis cts design flow. Ese566a modern systemonchip design, spring 2017 3 figure 4.
This is done using ccopt clock concurrent optimization from azurocadence. Repetto and vincenzo sinisi stmicroelectr onics, central cad and design solutions, 20041 agrate brianza, italy. Advanced asic chip synthesis using synopsys design. Clock tree synthesis for timing convergence and timing yield. In integrated circuit design, physical design is a step in the standard design cycle which follows. Compiler, taking the design of bes6799 chip under smic. Simulation and post synthesis simulation, synopsys design compiler. The cts821 warning is reported for any generated clock that can not be traced back to its master source.
B report the defined ndr rule and verify that the spacing. 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. Synthesis and scripting techniques for designing multi. Furthermore, the book contains indepth discussions on the basis of synopsys technology libraries and hdl coding styles, targeted towards optimal synthesis solution. I ntroduction clock tree synthesis cts is a critical stage of physical design, since clock network often constitutes a high percentage of the overall power in the final fullchip design.
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