Gate level simulation pdf

Gatelevel simulation of digital circuits using multi. The simulation semantics of conditional constructs in both hdl languages, verilog and vhdl, are insufficient to accurately model the ambiguity. There are many sources of trouble in gatelevel simulation. This book provides the reader with an extensive background in the field of logictiming simulation and delay modeling.

It means a test which takes x ns in rtl simulation will take the same amount in gate level simulations too. Pdf on jan 1, 2008, henri hakonen and others published elevator traffic simulation procedure find, read and cite all the research you need on researchgate. Gatelevel simulation methodology improving gatelevel simulation performance author. For designs greater than 100,000 gates, formalpro is an essential verification tool in an asic design flow. Gatelevel methodology customer survey carried out by cadence. The simulated system consists of 9 registers, 4 buses, 40 gates, an adder, a memory, a microprogrammed control subsystem, a 3phase clock, a scratch register. Pdf improving gatelevel simulation accuracy when unknowns exist. What are the benefits of doing gate level simulations in. There are many sources of trouble in gate level simulation. Gate level simulation of logical state preparation.

Logic simulation is currently one of the main verification tools in the design or verification engineers arsenal. In this simulation design example, the gatelevel netlist multiplier. Pdf unknown values xs may exist in a design due to uninitialized registers or blocks that are powered down. Using systemverilog assertions in gate level verification environments mark litterick, verilab, munich, germany. A different approach is given in 1, where a functionallevel mixedmode simulator is described. The simulation semantics of conditional constructs in both hdl languages, verilog and vhdl, are insufficient to accurately model the ambiguity inherent in uninitialized registers and power on reset values. The most difficult part in gate level simulation gls is x propagation debug. Gate level simulation may take up to onethird of the simulation time and could potentially take most of the debugging time. Gatelevel power and current simulation of cmos integrated circuits. Formalpro gatelevel regression testing of asics mentor. Gate level simulation is increasing trend tech trends. Eventdriven gatelevel logic simulation using a timing wheel data structure ece470 digital design ii imagine how the circuit in fig. Oct 05, 2018 gatelevel simulation dates back to a simpler time when ic designs were, well, simple. Gatelevel simulation with modelsimaltera simulatorverilog hdl.

Creating gate level schematics and simulation design architect and eldo. Event 201, a pandemic exercise to illustrate preparedness. It is run after rtl code is simulated and synthesized into a gate level netlist. Apr 01, 2017 top 50 vlsi ece technical interview questions and answers tutorial for fresher experienced videos duration. Improving gatelevel simulation of quantum circuits1 george f. Designs that take days or even weeks to simulate with gatelevel simulation can be verified in hours or even minutes using formalpro. Design architect is a leading cadeda tool from mentor graphics. Hence, gate level simulations are often used to determine whether scan chains are correct. Do not turn on run gate level simulation automatically. Gate level power and current simulation of cmos integrated circuits. It is run after rtl code is simulated and synthesized into a gatelevel netlist. Nov 27, 2011 please note although, gate level simulations take a lot of real time compare to rtl simulation, the time intervals in the test is the same. A fast gatelevel hdl simulation using higher level models dusung kim1 maciej ciesielski1 kyuho shim2 seiyang yang2 1department of electrical and computer engineering university of massachusetts, amherst, ma, usa 01003.

One method of facilitating gate level simulation includes generating crossreference instrumentation data including instrumentation logic indicative of an execution status of at least one synthesizable register transfer. Rtl design, verification, gls, systemc and ams top. The increase in design sizes and the complexity of timing checks at 40nm technology nodes and below is responsible for longer. Gate level synthesis involves implementing the behavior of the circuit described by a verilog model u sing standard gates. Gatelevel simulation with gpu computing debapriya chatterjee university of michigan andrew deorio university of michigan and valeria bertacco university of michigan functional veri. Eventdriven gatelevel logic simulation using a timing. In the quartus software, in the processing menu, point to start and click start analysis and synthesis. It will also look at some of the additional challenges that arise when running a gatelevel simulation with back. Using systemverilog assertions in gatelevel verification environments mark litterick, verilab, munich, germany.

All the device libraries required for this gatelevel simulation example come precompiled with the modelsimaltera software. Verify correctness of synthesized circuit verify synthesis tool delaytiming estimates synthesis tool generates. As of my knowledge every soc company is depending on gls, even after efficiently using rtl simulations, advancements in static verification tools like sta static tim. Logictiming simulation and the degradation delay model. This technique is orders of magnitude faster than traditional gate level simulation. For designs greater than 100,000 gates, formalpro is. Debugging the netlist simulations is a big challenge. Multiple debug iterations may happen in gls to find out many such flops. The most common form of logic simulation is known as event driven because, perhaps not surprisingly, these tools see the world as a series of discrete events. Logic simulation is the use of simulation software to predict the behavior of digital circuits and hardware description languages. This eliminates a manual process and offers manifold advantages that will be discussed in this papel. Vcs xprop is designed to help find xrelated issues at rtl and reduce the requirement for lengthy gatelevel simulations. For whatever reason, theres no tool to check such situation. Is gatelevel simulation still required nowadays verification horizons blog rss.

The increase in design sizes and the complexity of timing checks at 40nm technology nodes and below is responsible for longer run times, high memory requirements, and the need for a. It can be used to simulate gate level and transistor level circuits. In my experience, my testbench is running good on rtl simulations but on gate level simulations some problems suddenly appear like my assertions are failing because of glitches, sampling of data by the monitor is wrong, etc. In other words, the job of the gatelevel simulator is to apply an input vector at the abc primary inputs pis and compute the response values at the g. When the complexity of an integrated circuit design reaches the point where electrical analysis is no longer costeffective, logic simulation or gate level simulation may be used. What i need are the proper way on creating a testbench for a gate level simulation. Methods of instrumenting synthesizable source code to enable debugging support akin to highlevel language programming environments for gatelevel simulation are provided.

Yet, despite its age and relatively slow speeds, gatelevel simulation remains essential to meeting verification goals. When the complexity of an integrated circuit design reaches the point where electrical analysis is no longer costeffective, logic simulation or gatelevel. In this work we propose gcs, a solution to boost the performance of logic simulation, gate level simulation in particular, by more than a factor of 10 using recent hardware advances in graphic. Gatelevel simulation is also used to verify the powerup, powerdown and reset sequences of the full chip. In the category list, select simulation under eda tool settings. Mar 05, 2014 a transistor level b gate level c register transfer level rtl in many companies rtl simulations is the basic requirement to signoff design cycle, but lately there is an increasing trend in the industry 1 to run gate level simulations gls before going into the last stage of chip manufacturing. The johns hopkins center for health security in partnership with the world economic forum and the bill and melinda gates foundation hosted event 201, a high level pandemic exercise on october 18, 2019, in new york, ny.

In the tool name list, specify simulation tool as modelsim. Fast sta predictionbased gatelevel timing simulation. Even these cells are not defined in the liberty syntax. Apply gatelevel simulation the golden simulator at each step to verify functionality. Its a problem that we might be able to find in gate level simulation. Performing gate level simulation gives us the opportunity to check that our circuit still works properly after being synthesized and placed and routed. Pdf gatelevel simulation of logical state preparation. Tutorial for gate level simulation verification academy. In gls, models of the cells make the output x if there. Simulation can be performed at varying degrees of physical abstraction, such as at the transistor level, gate level, registertransfer level rtl, electronic system level esl, or behavioral level.

This series will look at examples of problems that can come from your library vendor, problems that come from the design, and problems that can come from synthesis. This is ok in rtl simulation, but with gls it causes everything to go x. If i understand correctly, you must be initialize the memory at the beginning of functional simulation not gate level simulation, your gate level simulation with notiming, should be same as functional simulation, the only difference will be, instead of rtl, you are picking up netlist and technology verilog file which required during. Improving gatelevel simulation of quantum circuits. In the tool name list, specify simulation tool as modelsimaltera. All the device libraries required for this gate level simulation example come precompiled with the modelsimaltera software. Standard delay format sdf file of estimated delays. Pdf gatelevel power and current simulation of cmos. Treat xgobblers as sketchy engineers like to put xgobblers on their gate simulation models like rams, fuses, and plls because the ram model authors love to drive xs out of their ram. Index terms gatelevel timing, static timing analysis, dynamic timing simulation. Top 50 vlsi ece technical interview questions and answers tutorial for fresher experienced videos duration.

I have been working in gls fullypartly since 2 years in one of the soc company. Noting the vast available parallelism in the hardware of modern gpus, and the inherently parallel structures of gatelevel netlists, we propose novel algorithms for. Increasing the size of the simulation to 9 qubits can double the number of gates used. In my experience, my testbench is running good on rtl simulations but on gate level simulations some problems suddenly appear like my.

Start a new quartus project using the project wizard and choose sums as the name of design and top module. In any design process the simulation of this gatelevel netlist will eventually shows the. In essence, logic analysis may be viewed as a simplification of timing. What are the benefits of doing gate level simulations in vlsi. It will also look at some of the additional challenges that arise when running a gate level simulation with back. Aug 03, 2016 i have been working in gls fullypartly since 2 years in one of the soc company.

About event 201, a highlevel pandemic exercise on october. I said might because it still depends on the timing relationship between async signals, which is actually a random thing from simulation point of view. In the processing menu, point to start and click on start eda netlist writer. In gate level synthesis, the verilog file is synthesized into a netlist file which includes standard gates and their delays. In this tutorial, we will be using design architect to implement a nor gate shown below, and simulate it using. Even today, gatelevel simulation is still a major signoff step for most semiconductor projects. As an example, consider a very simple circuit comprising an or gate driving both a buf buffer gate and a brace of not. However, those simulations can take days or weeks to run.

Eventdriven gatelevel logic simulation using a timing wheel. The simulation takes place at the register, bus, and gate level. Designs that take days or even weeks to simulate with gate level simulation can be verified in hours or even minutes using formalpro. Simulation is critical for early evaluation of implementation approaches and prototypes yet remains a signi. A necessary evil part 1 rising complexity, tightening schedules and ever demanding time to market pressure are pushing the industry to move to the next level of abstraction for design representation viz esl electronic system level.

Performing gatelevel simulation gives us the opportunity to check that our circuit still works properly after being synthesized and placed and routed. This technique is orders of magnitude faster than traditional gatelevel simulation. Zero delay elements in logic simulation sciencedirect. Using systemverilog assertions in gatelevel verification. Rather than dealing with voltages and currents at signal nodes, discrete logic states are used. You can use this design example to learn how to perform gatelevel timing simulations of your design implemented in stratix ii devices with the cadence ncsim simulator. Dec 16, 20 compile time switches that are usually used in gatesim. Gatelevel simulation with modelsimaltera simulator. Verify the specification through simulation or verification. Additionally, we use the gate level simulations to obtain switching activies for each gate in the design. X propagation in gls is mostly caused by x pessimism, so it is practical to suppress them and focus on the main purpose of gls.