Linting and its Importance in RTL Design

 Linting is a process of Static code analysis of the RTL design, to check the quality of the code using thousands of guidelines/rules, based on some good coding practice. When these guidelines are violated, the lint tool raises a flag either for review or waiver by design engineers. This is done before simulation once the RTL design is ready.  The main objective of doing linting is to come up with a clean RTL before proceeding into the lengthy back end stages in the ASIC Design Cycle. This process reduces the synthesis errors and functional bugs in the design. Also, it improves the coding styles for readability and reduces synthesis and simulation mismatch issues. 

Linting provides an insight into the RTL code at the early stage of a design. Linting saves a good amount of time by identifying coding mistakes and recommending a fix at the initial stage of a design thereby boosting the confidence of the RTL Design Engineer. Below are some examples of problems it addresses and raises a flag accordingly.

• Are there any unintentional Latches?
• Are there any set/reset conflicts?
• Are there any Out of Range indexing?
• Are there any combinational loops in the design?.
• Are there any multi-driven ports/nets in the design?.
• Are there any non-synthesizable blocks in the design?
• Are there any undriven nets in the design?
• Are there any asynchronous resets in the design?

Lint can identify many errors that may or may not be caught by the functional simulators. If lint is not performed for a design before passing it to the synthesis team, there is a high possibility that it causes issues during synthesis, which could be due to some unintentional combinational loops, non-synthesizable code, and multi-driven nets. As it costs a lot in terms of time and design resources if the RTL design has to go through the same design phases again due to some bugs found at the later stages of a design flow.

A list of some Lint Tools used in the VLSI industry is given below.

• SPYGLASS from Synopsys
• GASPER GOLD from Cadence
• ALINT PRO from Aldec
• Mentor Graphics (inbuilt with HDL Designer)

Verification Vs Validation In VLSI

 

State of the art SOC designs is so complex that, coming up with a bug-free design is very difficult. So chip design flow incorporates several steps to identify the bugs in the earlier stages as well as, in the later stages.

Verification and Validation, both probe for the correctness of the design against the specification by identifying and localizing the bugs in the system, but at different stages in the design cycle. Verification is a pre-silicon process of checking the functionality of the design by simulating it whereas, Validation is a post-silicon process of finding bugs in a few initially manufactured prototypes in the context of a system.

Verification

Functional verification is the process of demonstrating the functional correctness of an RTL design with respect to the design specifications. Functional verification attempts to check whether the proposed design is doing what it is intended to do. This is a complex task and takes the majority of time and effort in most large electronic system design projects. It is imperative that the design is functionally verified and any potential bug is eliminated at an early stage.

It is very common that more engineers’ time and expense is spent to verify a design than the rest of the steps in the ASIC design cycle. Even with this large expenditure, most designs are first fabricated with several bugs still in them. So here comes the importance of Validation.

Validation

While pre-silicon verification runs the test cases on the design on the simulator, post-silicon validation is executed on a few initial hardware prototypes of the design on the silicon chip in a real environment. This process captures the bugs that are escaped during the RTL Design Verification phase. Validation also checks for the correctness of the design but on the real hardware in an actual working ambience.

When a design is passed through all the steps in the design cycle, a few initial prototypes are fabricated as test prototypes. These prototypes are mounted on a test board in a real working environment with real test speed. Identifying bugs through validation is a very fast process as compared to the design verification process but it is difficult to debug the design as there is no way to access the internal signals.

What is Unateness in Static Timing Analysis?

Timing Sense corresponds to the functionality of the standard cells. It explains the traversal of a data from the source pin of the gate to its sink pin. Timing sense is also called as unateness of the timing arc.

All the standard cells can be classified based on the unateness they possess. Positive unate, Negative unate and Non-unate are the three types of unateness.

Under the timing section of a standard cell in a .lib file, you can find timing sense information.  

Positive unate: The rise transition at the source pin causes rise transition or no transition at the sink pin and fall transition at the source pin causes fall transition or no transition at the sink pin.

Standard Cells like AND Gate, OR gate, buffer possess this property.

Consider the truth table of AND Gate:

Consider the 1st case of inputs where both A and B are at logic 0 and output is at logic 0. Now consider B is getting transition to logic 1 then the output remains at logic 0 only (no transition). Now let A change to logic 1 then the output also transitions to logic 1.

Negative unate timing arc: The rise transition at the source pin causes fall transition or no transition at the sink pin and fall transition at the source pin causes rise transition or no transition at the sink pin.

Standard Cells like NAND Gate, NOR gate, inverter possess this property.

Consider the truth table of Inverter:

Signal transition on input A makes an opposite transition on the output pin Y.

Non unate: A standard cell which does not possess either of the property is said to be non-unate. XOR and XNOR gates have non-unate timing arcs.

Consider the truth table of XOR Gate :

Consider the 1st case of inputs where both A and B are at logic 0 and output is at logic 0. Now consider B is getting transition to logic 1 then the output changes to logic 1. Consider the 3rd row, where output is at logic 1 with A at logic 1 and B at logic 0, now let B change to logic 1 then the output transitions to logic 0. The gate does not possess either of the property. Hence the timing sense of XOR gate is non-unate.  

How To Choose Frontend Vs. Backend? A guide for Freshers

 

#VLSI frontend and backend are nothing but two different domains in the field of VLSI.

The classification is based on the different steps involved in a typical ASIC design flow. The following diagram shows a typical design flow for an ASIC or SOC.

As it shows the design flow starts with a specification document that lists out the technical requirements needed in the chip design. It is followed by translating the specification to Architectural design. The architectural design involves designing the functional blocks and the communication protocol between them and translating them into actual modules that contain FSMs, combinational and sequential circuits, etc. The architectural design is then modeled using a Hardware description language like Verilog/VHDL/System Verilog, which is the RTL design stage. The Functional Verification stage starts with a verification plan and a corresponding verification environment that describes and implements the method of proving the design correctness, using different Verification techniques. The design is refined until the HDL model is proved to be meeting the specifications. This stage is followed by Synthesis – a process of transforming the HDL design into a technology-specific gate-level netlist, given all the specified constraints and optimization settings. DFT is a structural technique that facilitates a design to become testable after production. All the works till this stage are normally called as the Frontend of VLSI design and are executed by Frontend Engineers.

The next step in the ASIC Design flow is Placement and Routing which involves arranging approximate locations of a set of modules that need to be placed on a layout. Clock tree synthesis is a process that makes sure that the clock gets distributed evenly to all sequential elements in a design to fix the timing violations. This is followed by routing in which exact paths for the interconnection of standard cells and macros and I/O pins are determined. The file produced at the output of the layout is the GDSII (GDS2) file which is the file used by the foundry to fabricate the silicon. Gate level simulations and Static Timing Analysis (a method of validating the timing performance of a design by checking all possible paths for timing violations without having to simulate) are also done to make sure that the gate-level design meets the timing requirements for correct design operations. All steps after logic synthesis are performed by Backend engineers and form the Backend jobs.

Work of a Frontend Engineer

• RTL Design/Coding
• Synthesis
• Functional Verification
• DFT
• Work of a Backend Engineer
• Floor Planning
• Placement
• Clock Tree Synthesis
• STA
• Physical Verification

Which one has more career Opportunities?

With the advances being made in technologies like process geometries, feature size, and product innovations on a daily basis, there is a constant need to design, develop, and re-engineer integrated circuits (ICs). Since electronic products like mobile phones are being released with new features in shorter cycles, there is a healthy demand for qualified VLSI engineers to work on these products. Therefore, there is a good scope for a career in the VLSI industry.

The important point is that both the domains, front end, and back end have their own advantages and have great career prospects. It is completely up to you which one to choose depending on your interest and confidence level, as both offer a great deal of learning and growth.

How to choose?

In order to become a front end engineer, one needs to have good knowledge of HDLs(Verilog/VHDL/SystemVerilog). It will be an added advantage if you have industry related protocol knowledge.

So if you have ample digital fundamental knowledge, are fond of HDL coding, love debugging, and want to have a sound understanding about the functionality of IC or chip you should definitely go for Front End. With the recent emergence of Artificial intelligence and its application towards VLSI opens up huge scope for Front end engineers.

In order to become a back end engineer, one needs to be well equipped with the concepts of digital electronics, CMOS and Analog Circuits, Scripting knowledge for automation, Hands-on Tools for physical design, layout, etc.

If the above-mentioned skills fascinate you then you can opt for Backend and there might be a chance to work in Foundry as well.

Challenges faced by a fresher to get into the VLSI industry

Even though the VLSI industry is a niche and has lots of career opportunities, on the flip side, the industry is currently somewhat less reachable for fresh graduates, compared to other areas due to some particular reasons. Firstly, VLSI or chip design requires a deeper level of knowledge and skills than other electronics-related fields. But our Universities are not catering 100% to the VLSI industry requirements. Secondly, VLSI chip design is expensive and requires access to high-cost, specialized electronic design automation (EDA) tools.

How can Chipedge help?

Chipedge offers various courses for fresh graduates both in frontend and backend domains, to choose from. The courses are well structured starting from building a strong foundation by emphasizing fundamental subjects like Digital, CMOS, etc. Once the candidate becomes confident with the fundamental knowledge, we impart all the domain-specific skills required for the VLSI industry, by giving hands-on training on industry-standard EDA tools (Synopsys).

The Future of Very Large-Scale Integration (VLSI) Technology

The verifiable development of IC registering power has significantly changed the manner in which make process, convey, and store data. The motor of this exceptional development is the capacity to recoil transistor measurements at regular intervals. This pattern, known as Moore's law, has proceeded for as far back as 50 years. The anticipated destruction of Moore's law has been more than once refuted gratitude to innovative leaps forward (e.g., optical goals improvement procedures, high-k metal entryways, multi-door transistors, completely exhausted ultra-dainty body innovation and 3-D wafer stacking).

In any case, it is anticipated through the VLSI course in Bangalore that in a couple of decades, transistor measurements will arrive at a point where it will get uneconomical to recoil them any further, which will in the long run bring about the finish of the CMOS scaling guide. This exposition examines the potential and constraints of a few post-CMOS up-and-comers right now being sought after by the gadget network.

·    Soak transistors: The capacity to scale a transistor's inventory voltage is controlled by the base voltage required to turn the gadget between an on-and an off-state. The sub-limit incline (SS) is the measure used to demonstrate this property. For example, a littler SS implies the transistor can be turned on utilizing a littler inventory voltage while meeting the equivalent off current. For MOSFETs, the SS must be more noteworthy than ln(10) × kT/q where k is the Boltzmann steady, T is the supreme temperature, and q is the electron charge. This essential limitation emerges from the thermionic idea of the MOSFET conduction component and prompts a principal power/execution tradeoff, which could be survived if SS esteems altogether lower than the hypothetical 60-mV/decade breaking point could be accomplished. Numerous gadget types have been suggested that could create soak SS esteems, including burrowing field-impact transistors (TFETs), nanoelectromechanical framework (NEMS) gadgets, ferroelectric-entryway FETs, and effect ionization MOSFETs. A few late papers have detailed test perception of SS esteems in TFETs as low as 40 mV/decade at room temperature. These alleged "soak" gadgets' fundamental constraints are their low versatility, hilter kilter drive current, predisposition subordinate SS, and bigger measurable varieties in contrast with conventional MOSFETs.

·    Turn gadgets:Spintronics is an innovation that uses nano magnets' turn bearing as the state variable. Spintronics has one of a kind properties over CMOS, including nonvolatility, lower gadget check, and the potential for non-Boolean figuring models. Spintronics gadgets' nonvolatility empowers moment processor wake-up and shut down that could drastically decrease the static force utilization. Besides, it can empower novel processor-in-memory or rationale in-memory structures that are impractical with silicon innovation. Despite the fact that in its early stages, explore in spintronics has been picking up energy over the previous decade, as these gadgets might defeat the force bottleneck of CMOS scaling by offering a totally new registering worldview. As of late, progress has been made toward showing of different post-CMOS spintronic gadgets including all-turn rationale, turn wave gadgets, space divider magnets for rationale applications, and turn move torque magnetoresistive RAM (STT-MRAM) and turn Hall torque (SHT) MRAM for memory applications. In any case, for spintronics innovation to turn into a practical post-CMOS gadget stage, specialists must discover approaches to dispense with the transistors required to drive the clock and force supply signals. Something else, the presentation will consistently be restricted by CMOS innovation. Other outstanding difficulties for spintronics gadgets incorporate their moderately high dynamic force, short interconnect separation, and complex creation process.

·    Adaptable hardware: Distributed enormous region (cm2-to-m2) electronic frameworks dependent on adaptable meager film-transistor (TFT) innovation are attracting a lot of consideration because of one of a kind properties, for example, mechanical comparability, low temperature processability, huge region inclusion, and low manufacture costs. The DFT course recommends different types of adaptable TFTs can either empower applications that were not feasible utilizing conventional silicon based innovation, or outperform them regarding cost per region. Adaptable gadgets can't coordinate the exhibition of silicon-based ICs because of the low transporter versatility. Rather, this innovation is intended to supplement them by empowering appropriated sensor frameworks over an enormous zone with moderate execution (under 1 MHz). Advancement of inkjet or move to-move printing strategies for adaptable TFTs is in progress for ease fabricating, making item level executions plausible. Regardless of these empowering new advancements, the low versatility and high affectability to handling parameters present significant creation challenges for acknowledging adaptable electronic frameworks.

CMOS scaling is reaching a conclusion, however no single innovation has risen as an unmistakable successor to silicon. The critical requirement for post-CMOS choices will keep on driving high-chance, high-result look into on novel gadget advances. Duplicating silicon's prosperity may seem like an unrealistic fantasy. In any case, with the world's ideal and most splendid personalities at work, we have motivations to be hopeful.

The Business and Organizations are extending with VLSI as a relative Ascent with Time

The business and organizations are extending with VLSI as a relative ascent with time

VLSI [Very-large scale integration] is a chip-plan, a kind of a strategy that creates coordinated circuits by interfacing a huge number of transistor-based circuits into the single chip. It can rapidly look through an application in Communications, DSP, Microwave and RF, Cryptography, MEMS, Automobiles, Consumer Electronics, Robotics, Space Applications, and Health industry. 

Today, VLSI courses are seen wherever around us. Progressed VLSI chips can be found in our mobile phones, vehicles, family unit machines, restorative gadgets, cameras, and numerous other electronic articles. 

Right now, examine everything you have to think about VLSI Training. Requirement For VLSI Training: 

As innovation propels, the benefits of VLSI have made it one of the basic components to drive gadgets around us. Vehicles, Cell telephones, home machines, and furthermore devices or medicinal gadgets have progressed VLSI fitted in them. Something else that pulls in students is that there are odds of high paid occupations right now. In any case, just a straightforward science certificate can't get you to join the VLSI structuring work. You need to ace various different abilities when you take a crack at a VLSI plan course. This is the motivation behind why numerous alumni join the VLSI Training course. 

Step by step instructions to Enroll In VLSI Training ?

The preparation program needs hands-on demo and mastery and for that, you require to join a presumed VLSI Training classes In Delhi which can offer you great mentors and have different sorts of hardware required. The primary thing you require to do is note down the best organizations offering the VLSI configuration preparing program. The consequent advance would think about among them dependent on your span, course type, area, expenses, grounds choice, affirmation, work help, and so on. You ought to consistently look for an organization which offers you with arrangement after the finishing of the preparation. 

Subsequent to contrasting, you require to do further research with respect to the one which is best for you. There is a more straightforward way nowadays for that which is online surveys and evaluations. You get an extremely exact information on what the past students have cherished and abhorred about the foundation. It is exceptionally fundamental to ensure that solitary specialists educate in the organization. Experience the site of the organization to get further information and see its areas of aptitude. At long last, if everything appears to you guaranteeing that is the preparation organization for you. 

To put it plainly, steps 

• Select the best organization for VLSI Training according to your need and prerequisite   by looking at changed VLSI establishment on different parameters. 

• In the wake of choosing the foundation, you can either try out their homeroom preparing   program or web based preparing program. 

• Additionally, you can either go for 4/a month and a half preparing or a half year   preparing according to your benefit. 

• Once, you take a crack at the program, you will get the chance to chip away at live   undertaking. 

• After the culmination of your course, you will get endorsement of fruition which will   improve estimation of your resume. 

• You will likewise be guaranteed situation help after consummation of your preparation   and opportunity to show up in position drive of rumored organizations. 

• Vocation Prospect After VLSI Training : 

• VLSI Designers are normally procured by the organizations engaged with the   accompanying spaces – 

• Electricals 

• Media transmission 

• Hardware 

• Instrumentation 

• Registering 

• Data Technology 

• Mechanization 

• Generation Control 

• Consultancy 

• In the previously mentioned firms, one may do jobs, for example, – 

• VLSI Designer 

• VLSI Programmer 

• VLSI Project Manager 

• VLSI Consultant 

• VLSI R&D proficient 

• 6 Advantages of VLSI Training 

• Diminishes the size of the circuits. 

• Diminishes the real expense of the gadgets. 

• Improves the circuits working rate 

• Needs less force when contrasted and discrete parts. 

• Fantastic unwavering quality 

• Occupies a nearly little room. 

Conclusion

At last, we can infer that expert preparing causes you in accomplishing your particular goals, advancement or simply gaining extra abilities. Picking the correct course and the correct organization is the starting square to make a way prompting achievement.

VLSI Design Is An Up And Coming Innovation All Together And Developing In India

These courses spread the diagram of VLSI and clarify VLSI innovation, SoC structure, Moores law, and the contrast among ASIC and FPGA. With this outline, it strolls you through every one of the means of complete the VLSI Design stream and clarifies each progression in detail in VLSI design course online. At that point, it covers the whole computerized structure, combinational, consecutive, and FSM plans. Lastly, it trains you widely on Verilog HDL programming and makes you a hands-on RTL originator.

The advantages of this Online VLSI Course are: 

- Affordable Online VLSI Course 

- Online course with Projects, Labs and backing material* 

- Course Delivered by Industry Experts 

- A certificate with Grade on fruitful fulfillment of the course 

- Avail grant on affirmation for work situated Advanced homeroom courses 

Design is quick, application explicit, An entire framework on a single chip, chip sizes may fluctuate yet. 

VLSI configuration decreases the region of the circuit, additionally with more affordable and having less force dispersal line guideline factors of both electronic and straightforward circuits.  

The principal issue in the present world is power scattering and supply voltage. Be that as it may, in VLSI, we chiefly focus on these segments.  

To be a section VLSI industry, we require a solid direction on the nuts and bolts of digital and straightforward circuits. 

It is a blast Course that is exceptionally favored by gadgets, and electrical understudies who are keen on Embedded Systems and VLSI course can participate in the Moschip Institute of Silicon Systems(M-ISS). They are going to begin their course from August fifth,2019, from Embedded Training in PUNE.  

If you get some information about VLSI Design, they will begin talking about 1lac transistors implanted in a specific chip various things. Nobody could get a clear picture of what's about VLSI.  

I'll make it a basic definition for you on VLSI. The methodology required to produce a coordinated circuit is VLSI Design. The IC might be Digital, Analog, or Mixed one that doesn't have a lot of effects.

The accompanying methods, for example, 

·         Front End IC plan and Verification 

 

·         FPGA Prototyping 

 

·         SoC or Firmware Verification 

 

·         Plan for Testability (DFT) 

 

·         Low Power Verification 

 

·         Physical Design (BackEnd Design) 

 

·         Veil creation 

 

·         Photolithography 

 

·         Scratching 

 

·         Manufacture 

 

·         Bundling 

 

·         Testing 

 

·         Application testing 

 

These all the abovementioned and a lot more sub exercises go under VLSI. 

When all is said in done, the Design to Manufacturing procedure of an IC can be expressed as VLSI Design as per my experience. 

we have seen a significant four classified ages of IC's  

1.SSI ( Small Scale Integration) 

2.MSI ( Medium Scale Integration) 

3.LSI ( Large Scale Integration) 

4.VLSI ( Very Large Scale Integration) 

Presently we are in our fifth and last age of the incorporated circuits(ULSI). 

The parts utilized in Electronic Circuits like diode were comprised of vacuum tubes and were called discrete segments. Later, when the Solid State Device(SSD) was concocted, the parts were included in semiconductors.