The concept of modularity enables parallelization of the design process. Locality: The concept of locality in system ensures that the internal details of each Answer: VLSI Design flow consists of several steps which are carried out in linear . VLSI Design Methodologies EEB (Winter ): Lecture # 4Mani of Structured Design Techniques Hierarchy Regularity Modularity Locality; . architecture structure of accumulator is component reg — definition of. Digital VLSI Circuits. 1. Introduction to ASIC Design a. Design Strategies: Hierarchy, Regularity, Modularity & Locality b. Chip Design Options: Gate Array, Field.

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It is mapped onto the chip surface by floorplanning. The signal delay, noise margins, and power consumption of each cell should be also optimized with proper sizing of transistors using circuit simulation.

Locality By defining well-characterized interfaces for a module, we are stating that any other internal detail is unimportant to any parent module. However, the development cost of such a design style is becoming prohibitively high.

Design of VLSI Systems – Chapter 1

The last evolution involves a detailed Boolean description of leaf cells followed by a transistor level implementation of leaf cells and mask generation. As in the gate array case, neighboring transistors can be customized using a metal mask to form basic logic gates. The designer attempts to divide the hierarchy into a set of similar blocks. Thus, it can generate any function of up to four variables or any two functions of three variables.

Hierarchy Rules for Layout

Remember that diffusion spacing rules are likely to be greater than metal spacing rules. Modularity in design means that the various functional blocks which make up the comcept system must have well-defined functions and interfaces. Regularity means that the hierarchical decomposition of a large system should result in not only simple, but also similar blocks, as much as possible.


The Y-chart first introduced by D. The LUT is a digital memory that stores the truth table of the Boolean function. Thus, the concept of design reuse is becoming popular in order to reduce design cycle time and development cost.

In the case of layout, we must avoid making unwanted connections to elements in the sub-module and we must avoid design ,ocality violations caused by the proximity of external elements to internal elements.

In such a case, in order to fit the architecture into the allowable chip area, some functions may have to be removed and the design process must be repeated. Since no physical manufacturing step is necessary for customizing the FPGA chip, a functional sample can be obtained almost as soon as the design is mapped into a specific technology.

For logic chip design, a good compromise can be achieved by using a combination of different design styles on the same chip, such as moeularity cells, data-path cells and PLAs. Complexity Control Hierarchy is used to simplify the kn of complex systems.

Internal elements within the cell should be at least one half of one design rule distance inside the cell boundary.

It starts with a given set of requirements. As an example of structural hierarchy, Fig.

Hierarchy Rules for Layout

These modules are then geometrically placed onto the chip surface using CAD tools for automatic module placement followed by routing, with a goal of minimizing the interconnects area and signal delays. The magic router also supports the labelling style shown below which uses rectangles for port labels: Here, the numbers for circuit complexity should be interpreted only as representative examples to show the order-of-magnitude.


The programming of the chip remains valid as long as the chip is powered-on, or until new programming is done. Memory banks RAM cachedata-path units consisting of bit-slice cells, control circuitry mainly consisting of standard cells and PLA blocks.

For locality to work, we must impose restrictions on the use of a sub-module. Hierarchy, regularity, modularity and locality. Thus two diffusions must be separated by 0. If necessary, the replication of some logic may solve this problem in large system architectures.

Wiring should not normally overlap a comcept. The keep out area for each layer should extend for one half of one design rule distance beyond the edge of the cell. Point labels may be used to label internal nodes that are not intended as ports. The typical design flow of an FPGA chip starts with the behavioral description of its functionality, using a hardware description language such as VHDL.

As a result, the level of actual logic integration tends to fall short of the integration level achievable with the current processing technology.