Gate level simulation pdf

Eventdriven gatelevel logic simulation using a timing. Rtl design, verification, gls, systemc and ams top. Logic simulation is currently one of the main verification tools in the design or verification engineers arsenal. 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. Pdf gatelevel power and current simulation of cmos. Using systemverilog assertions in gatelevel verification environments mark litterick, verilab, munich, germany. 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. The most difficult part in gate level simulation gls is x propagation debug. 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. 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. 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. It is also used to estimate dynamic power drawn by the. For designs greater than 100,000 gates, formalpro is.

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. It can be used to simulate gate level and transistor level circuits. Creating gate level schematics and simulation design architect and eldo. Performing gate level simulation gives us the opportunity to check that our circuit still works properly after being synthesized and placed and routed.

The increase in design sizes and the complexity of timing checks at 40nm technology nodes and below is responsible for longer. Verify correctness of synthesized circuit verify synthesis tool delaytiming estimates synthesis tool generates. In the quartus software, in the processing menu, point to start and click start analysis and synthesis. 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.

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. When the complexity of an integrated circuit design reaches the point where electrical analysis is no longer costeffective, logic simulation or gatelevel. Debugging the netlist simulations is a big challenge. 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. Pdf improving gatelevel simulation accuracy when unknowns exist. Apr 01, 2017 top 50 vlsi ece technical interview questions and answers tutorial for fresher experienced videos duration. Gatelevel simulation with modelsimaltera simulatorverilog hdl. Design architect is a leading cadeda tool from mentor graphics.

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. Noting the vast available parallelism in the hardware of modern gpus, and the inherently parallel structures of gatelevel netlists, we propose novel algorithms for. It means a test which takes x ns in rtl simulation will take the same amount in gate level simulations too. All the device libraries required for this gate level simulation example come precompiled with the modelsimaltera software. What are the benefits of doing gate level simulations in. All the device libraries required for this gatelevel simulation example come precompiled with the modelsimaltera software.

Even these cells are not defined in the liberty syntax. Fast sta predictionbased gatelevel timing simulation. Methods of instrumenting synthesizable source code to enable debugging support akin to highlevel language programming environments for gatelevel simulation are provided. Gate level simulation is increasing trend tech trends. Gate level simulation may take up to onethird of the simulation time and could potentially take most of the debugging time. 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. 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. Hence, gate level simulations are often used to determine whether scan chains are correct.

Is gatelevel simulation still required nowadays verification horizons blog rss. In any design process the simulation of this gatelevel netlist will eventually shows the. 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 essence, logic analysis may be viewed as a simplification of timing. In gate level synthesis, the verilog file is synthesized into a netlist file which includes standard gates and their delays. Using systemverilog assertions in gate level verification environments mark litterick, verilab, munich, germany. This eliminates a manual process and offers manifold advantages that will be discussed in this papel. Simulation is critical for early evaluation of implementation approaches and prototypes yet remains a signi. Formalpro gatelevel regression testing of asics mentor. This book provides the reader with an extensive background in the field of logictiming simulation and delay modeling. Designs that take days or even weeks to simulate with gatelevel simulation can be verified in hours or even minutes using formalpro. However, those simulations can take days or weeks to run. For whatever reason, theres no tool to check such situation.

It is run after rtl code is simulated and synthesized into a gatelevel netlist. 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. Pdf gatelevel simulation of logical state preparation. Designs that take days or even weeks to simulate with gate level simulation can be verified in hours or even minutes using formalpro. Multiple debug iterations may happen in gls to find out many such flops. In the tool name list, specify simulation tool as modelsim.

Aug 03, 2016 i have been working in gls fullypartly since 2 years in one of the soc company. In the category list, select simulation under eda tool settings. Standard delay format sdf file of estimated delays. 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. What are the benefits of doing gate level simulations in vlsi. 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. 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. Apply gatelevel simulation the golden simulator at each step to verify functionality. Additionally, we use the gate level simulations to obtain switching activies for each gate in the design. In gls, models of the cells make the output x if there. What i need are the proper way on creating a testbench for a gate level simulation.

Even today, gatelevel simulation is still a major signoff step for most semiconductor projects. Gatelevel simulation with gpu computing debapriya chatterjee university of michigan andrew deorio university of michigan and valeria bertacco university of michigan functional veri. As an example, consider a very simple circuit comprising an or gate driving both a buf buffer gate and a brace of not. There are many sources of trouble in gatelevel simulation. In my experience, my testbench is running good on rtl simulations but on gate level simulations some problems suddenly appear like my. Top 50 vlsi ece technical interview questions and answers tutorial for fresher experienced videos duration. About event 201, a highlevel pandemic exercise on october. Gatelevel simulation is also used to verify the powerup, powerdown and reset sequences of the full chip. Performing gatelevel simulation gives us the opportunity to check that our circuit still works properly after being synthesized and placed and routed. For designs greater than 100,000 gates, formalpro is an essential verification tool in an asic design flow. Oct 05, 2018 gatelevel simulation dates back to a simpler time when ic designs were, well, simple. Using systemverilog assertions in gatelevel verification. Gatelevel simulation methodology improving gatelevel simulation performance author.

Rather than dealing with voltages and currents at signal nodes, discrete logic states are used. 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. 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 tool name list, specify simulation tool as modelsimaltera. Its a problem that we might be able to find in gate level simulation. Logic simulation is the use of simulation software to predict the behavior of digital circuits and hardware description languages. Eventdriven gatelevel logic simulation using a timing wheel data structure ece470 digital design ii imagine how the circuit in fig.

In this tutorial, we will be using design architect to implement a nor gate shown below, and simulate it using. Gatelevel methodology customer survey carried out by cadence. This technique is orders of magnitude faster than traditional gatelevel simulation. 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. If the gate level simulation with sdf is done without a complete synchronizer list, then failure debug to find such cases on gate level is quite cumbersome.

It will also look at some of the additional challenges that arise when running a gate level simulation with back. It will also look at some of the additional challenges that arise when running a gatelevel simulation with back. Do not turn on run gate level simulation automatically. This is ok in rtl simulation, but with gls it causes everything to go x. The simulation takes place at the register, bus, and gate level. There are many sources of trouble in gate level simulation. Event 201, a pandemic exercise to illustrate preparedness. Tutorial for gate level simulation verification academy. Gate level simulation of logical state preparation. 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.

This technique is orders of magnitude faster than traditional gate level simulation. A different approach is given in 1, where a functionallevel mixedmode simulator is described. Gatelevel power and current simulation of cmos integrated circuits. Verify the specification through simulation or verification. Yet, despite its age and relatively slow speeds, gatelevel simulation remains essential to meeting verification goals. It includes detailed information on the challenges of logictiming simulation, applications, advantages and drawbacks. The simulation semantics of conditional constructs in both hdl languages, verilog and vhdl, are insufficient to accurately model the ambiguity. Gatelevel simulation with modelsimaltera simulator.

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. Improving gatelevel simulation of quantum circuits1 george f. Eventdriven gatelevel logic simulation using a timing wheel. Index terms gatelevel timing, static timing analysis, dynamic timing simulation. I have been working in gls fullypartly since 2 years in one of the soc company. It is run after rtl code is simulated and synthesized into a gate level netlist. Increasing the size of the simulation to 9 qubits can double the number of gates used. Vcs xprop is designed to help find xrelated issues at rtl and reduce the requirement for lengthy gatelevel simulations. Zero delay elements in logic simulation sciencedirect. Gate level simulation methodology improving gate level simulation performance author. In the processing menu, point to start and click on start eda netlist writer. 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.