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Signoff (electronic Design Automation)
In the automated design of integrated circuits, signoff (also written as sign-off) checks is the collective name given to a series of verification steps that the design must pass before it can be taped out. This implies an iterative process involving incremental fixes across the board using one or more check types, and then retesting the design. There are two types of sign-off's: front-end sign-off and back-end sign-off. After back-end sign-off the chip goes to fabrication. After listing out all the features in the specification, the verification engineer will write coverage for those features to identify bugs, and send back the RTL design to the designer. Bugs, or defects, can include issues like missing features (comparing the layout to the specification), errors in design (typo and functional errors), etc. When the coverage reaches a maximum% then the verification team will sign it off. By using a methodology like UVM, OVM, or VMM, the verification team develops a reusable envi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electronic Design Automation
Electronic design automation (EDA), also referred to as electronic computer-aided design (ECAD), is a category of software tools for designing Electronics, electronic systems such as integrated circuits and printed circuit boards. The tools work together in a Design flow (EDA), design flow that chip designers use to design and analyze entire semiconductor chips. Since a modern semiconductor chip can have billions of components, EDA tools are essential for their design; this article in particular describes EDA specifically with respect to integrated circuits (ICs). History Early days Prior to the development of EDA, integrated circuits were designed by hand and manually laid out. Some advanced shops used geometric software to generate tapes for a Gerber format, Gerber photoplotter, responsible for generating a monochromatic exposure image, but even those copied digital recordings of mechanically drawn components. The process was fundamentally graphic, with the translation f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Netlist
In electronic design, a netlist is a description of the connectivity of an electronic circuit. In its simplest form, a netlist consists of a list of the electronic components in a circuit and a list of the nodes they are connected to. A network (net) is a collection of two or more interconnected components. The structure, complexity and representation of netlists can vary considerably, but the fundamental purpose of every netlist is to convey connectivity information. Netlists usually provide nothing more than instances, nodes, and perhaps some attributes of the components involved. If they express much more than this, they are usually considered to be a hardware description language such as Verilog or VHDL, or one of several languages specifically designed for input to simulators or hardware compilers (such as SPICE analog simulation netlists). Types of netlists Netlists can be: * Physical (based upon physical connections) or logical (based upon logical connections) ** For ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Register Transfer Level
In digital circuit design, register-transfer level (RTL) is a design abstraction which models a synchronous digital circuit in terms of the flow of digital signals (data) between hardware registers, and the logical operations performed on those signals. Register-transfer-level abstraction is used in hardware description languages (HDLs) like Verilog and VHDL to create high-level representations of a circuit, from which lower-level representations and ultimately actual wiring can be derived. Design at the RTL level is typical practice in modern digital design. Unlike in software compiler design, where the register-transfer level is an intermediate representation and at the lowest level, the RTL level is the usual input that circuit designers operate on. In fact, in circuit synthesis, an intermediate language between the input register transfer level representation and the target netlist is sometimes used. Unlike in netlist, constructs such as cells, functions, and multi-bit re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clock Domain Crossing
In digital electronic design a clock domain crossing (CDC), or simply clock crossing, is the traversal of a signal in a synchronous digital circuit from one clock domain into another. If a signal does not assert long enough and is not registered, it may appear asynchronous on the incoming clock boundary. A synchronous system is composed of a single electronic oscillator that generates a clock signal, and its clock domain—the memory elements directly clocked by that signal from that oscillator, and the combinational logic attached to the outputs of those memory elements. Because of speed-of-light delays, timing skew, etc., the size of a clock domain in such a synchronous system is inversely proportional to the frequency of the clock. In early computers, typically all the digital logic ran in a single clock domain. Because of transmission line loss and distortion it is difficult to carry digital signals above 66 MHz on standard PCB traces (the clock signal is the highest fre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Functional Verification
In electronic design automation, functional verification is the task of verifying that the logic design conforms to specification. Functional verification attempts to answer the question "Does this proposed design do what is intended?" This is a complex task, and takes the majority of time and effort in most large electronic system design projects. Functional verification is a part of more encompassing ''design verification'', which, besides functional verification, considers non-functional aspects like timing, layout and power. Functional verification is very difficult because of the sheer volume of possible test-cases that exist in even a simple design. Frequently there are more than 10^80 possible tests to comprehensively verify a design – a number that is impossible to achieve in a lifetime. This effort is equivalent to program verification, and is NP-hard or even worse – and no solution has been found that works well in all cases. However, it can be attacked by many meth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromigration
Electromigration is the transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. The effect is important in applications where high direct current densities are used, such as in microelectronics and related structures. As the structure size in electronics such as integrated circuits (ICs) decreases, the practical significance of this effect increases. History The phenomenon of electromigration has been known for over 100 years, having been discovered by the French scientist Gerardin. The topic first became of practical interest during the late 1960s when packaged ICs first appeared. The earliest commercially available ICs failed in a mere three weeks of use from runaway electromigration, which led to a major industry effort to correct this problem. The first observation of electromigration in thin films was made by I. Blech.I. Blech: ''Electromigration in Thin Aluminum Fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SPICE
A spice is a seed, fruit, root, bark, or other plant substance primarily used for flavoring or coloring food. Spices are distinguished from herbs, which are the leaves, flowers, or stems of plants used for flavoring or as a garnish. Spices are sometimes used in medicine, religious rituals, cosmetics or perfume production. For example, vanilla is commonly used as an ingredient in fragrance manufacturing. A spice may be available in several forms: fresh, whole dried, or pre-ground dried. Generally, spices are dried. Spices may be ground into a powder for convenience. A whole dried spice has the longest shelf life, so it can be purchased and stored in larger amounts, making it cheaper on a per-serving basis. A fresh spice, such as ginger, is usually more flavorful than its dried form, but fresh spices are more expensive and have a much shorter shelf life. Some spices are not always available either fresh or whole, for example turmeric, and often must be purchased in ground form. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Process Corners
In semiconductor manufacturing, a process corner is an example of a design-of-experiments (DoE) technique that refers to a variation of fabrication parameters used in applying an integrated circuit design to a semiconductor wafer. Process corners represent the extremes of these parameter variations within which a circuit that has been etched onto the wafer must function correctly. A circuit running on devices fabricated at these process corners may run slower or faster than specified and at lower or higher temperatures and voltages, but if the circuit does not function at all at any of these process extremes the design is considered to have inadequate design margin. To verify the robustness of an integrated circuit design, semiconductor manufacturers will fabricate corner lots, which are groups of wafers that have had process parameters adjusted according to these extremes, and will then test the devices made from these special wafers at varying increments of environmental condi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clock Frequency
In computing, the clock rate or clock speed typically refers to the frequency at which the clock generator of a processor can generate pulses, which are used to synchronize the operations of its components, and is used as an indicator of the processor's speed. It is measured in the SI unit of frequency hertz (Hz). The clock rate of the first generation of computers was measured in hertz or kilohertz (kHz), the first personal computers (PCs) to arrive throughout the 1970s and 1980s had clock rates measured in megahertz (MHz), and in the 21st century the speed of modern CPUs is commonly advertised in gigahertz (GHz). This metric is most useful when comparing processors within the same family, holding constant other features that may affect performance. Determining factors Binning Manufacturers of modern processors typically charge premium prices for processors that operate at higher clock rates, a practice called binning. For a given CPU, the clock rates are determined at th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Statistical Static Timing Analysis
Conventional static timing analysis (STA) has been a stock analysis algorithm for the design of digital circuits over the last 30 years. However, in recent years the increased variation in semiconductor devices and interconnect has introduced a number of issues that cannot be handled by traditional (deterministic) STA. This has led to considerable research into statistical static timing analysis, which replaces the normal deterministic timing of gates and interconnects with probability distributions, and gives a distribution of possible circuit outcomes rather than a single outcome. Comparison with conventional STA Deterministic STA is popular for good reasons: *It requires no vectors, so it does not miss paths. *The run time is linear in circuit size (for the basic algorithm). *The result is conservative. *It typically uses some fairly simple libraries (typically delay and output slope as a function of input slope and output load). *It is easy to extend to incremental operation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Static Timing Analysis
Static timing analysis (STA) is a simulation method of computing the expected timing of a Synchronous circuit, synchronous digital circuit without requiring a simulation of the full circuit. High-performance integrated circuits have traditionally been characterized by the clock frequency at which they operate. Measuring the ability of a circuit to operate at the specified speed requires an ability to measure, during the design process, its delay at numerous steps. Moreover, delay calculation must be incorporated into the inner loop of timing optimizers at various phases of design, such as logic synthesis, layout (Placement (EDA), placement and Routing (EDA), routing), and in in-place optimizations performed late in the design cycle. While such timing measurements can theoretically be performed using a rigorous SPICE, circuit simulation, such an approach is liable to be too slow to be practical. Static timing analysis plays a vital role in facilitating the fast and reasonably ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Threshold Voltage
The threshold voltage, commonly abbreviated as Vth or VGS(th), of a field-effect transistor (FET) is the minimum gate-to-source voltage (VGS) that is needed to create a conducting path between the source and drain terminals. It is an important scaling factor to maintain power efficiency. When referring to a junction field-effect transistor (JFET), the threshold voltage is often called pinch-off voltage instead. This is somewhat confusing since ''pinch off'' applied to insulated-gate field-effect transistor (IGFET) refers to the channel pinching that leads to current saturation behaviour under high source–drain bias, even though the current is never off. Unlike ''pinch off'', the term ''threshold voltage'' is unambiguous and refers to the same concept in any field-effect transistor. Basic principles In n-channel ''enhancement-mode'' devices, a conductive channel does not exist naturally within the transistor, and a positive gate-to-source voltage is necessary to create one su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
