VLSI DESIGN STYLES

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INTRODUCTION TO VLSI and Y chart

Very-large scale integration (VLSI) is the process of incorporating thousands of transistors into a single chip to create an integrated circuit (IC) . VLSI got its start in the 1970s, when complex semiconductor and communication technologies were being developed. The microprocessor is a VLSI device. A limited set of functions were performed by most ICs prior to the introduction of VLSI technology. An electronic circuit contains a CPU, ROM, RAM, etc. IC designers can integrate all of these functions into a single chip using VLSI. Thanks to rapid advancements in large-scale integration technologies and device design applications, the electronics industry has grown at a breakneck rate in recent decades.Since the introduction of very large scale integration (VLSI) designs, the number of integrated circuits (ICs) used in high-performance computing, controllers, telecommunications, image and video processing, and consumer electronics has been increasingly growing...

VLSI Design Flow

Figure-: A simplified view of VLSI design flow. Figure depicts the VLSI design flow in a more condensed manner, taking into account the various design representations, or abstractions such as design- behavioural, logic, circuit, and mask layout. It's worth noting that concept verification is crucial at any stage of this procedure.Failure to properly verify a design in its early stages often results in substantial and costly re-design at a later level, increasing time-to-market. Although the design process has been represented in a linear fashion for ease of understanding, there are several iterations back and forth in practise, particularly between any two neighbouring steps, and sometimes even between pairs of steps that are far apart. Although top-down design flow is effective at controlling the design process, there i...

Design Hierarchy

The hierarchy, or 'divide and conquer' strategy, entails breaking down a subsystem into sub-modules and then repeating the process on the sub-modules until the smaller parts' complexity is manageable. This method is similar to how large programmes are broken down into smaller and smaller parts before simple subroutines with well-defined functions and interfaces can be written in software. It is nothing but dividing the task into smaller tasks until it reaches to its simplest level. This process is most suitable because the last evolution of design has become so simple that its manufacturing becomes easier. We can design the given task into the design flow process's domain (Behavioral, Structural, and Geometrical). To understand this, let’s take an example of designing a 16-bit adder, as shown in the figure below. Here, the whole chip of 16 bit adder is divided into four modules of 4-bit adders. Further, dividing the 4-bit adder into 1-bit adder or half adder. 1 bit a...

Concepts of Regularity, Modularity and Locality

By splitting the large structure into many sub-modules, the hierarchical design approach eliminates design complexity. To make the process easier, other design principles and approaches are usually needed. Regularity ensures that a large system's hierarchical decomposition can produce as many simple and identical blocks as possible.The design of array structures made up of similar cells, such as a parallel multiplication array, is a good example of regularity. Regularity can be seen at all levels of abstraction: uniformly sized transistors simplify the design at the transistor stage. Identical gate structures can be used at the logic level, and so on. The different functional blocks that make up the larger structure must have well-defined functions and interfaces, which is referred to as modularity in design. Since there is no doubt about the purpose and signal interface of these blocks, modularity allows each block or module to be co...

Field Programmable Gate Array (FPGA)

For chip implementation of specified algorithms or logic functions, a variety of design styles can be considered. Each design style has its own advantages and disadvantages, so designers must make an informed decision in order to provide functionality at a low cost. Field Programmable Gate Array (FPGA) The full form of FPGA is “ Field Programmable Gate Array ”. It s made up of tens of thousands to millions of logic gates with programmable interconnection. Programmable interconnections are available for users or designers to perform given functions easily. A typical model FPGA chip is shown in the given figure. There are I/O blocks, which are designed and numbered according to function. For each module of logic level composition, there are CLB’s (Configurable Logic Blocks) . CLB executes the logic operation that the module has been provided. The inter connection between CLB and I/O blocks are made with the help of horizontal routin...

Gate Array Design

In terms of quick prototyping capacity, the gate array (GA) comes in second after the FPGA. Metal mask design and processing are used for GA, while user programming is essential for the FPGA chip's design implementation. A two-step manufacturing process is needed for gate array implementation. On each GA chip, the first phase results in an array of uncommitted transistors. These uncommitted chips can be stored for later customization after the metal interconnects between the array's transistors are defined. The patterning of metallic interconnects occurs at the end of the chip fabrication process, allowing for a relatively quick turnaround period of a few days to a few weeks. Typical gate array platforms use dedicated areas called channels, for inter-cell routing between rows or columns of MOS transistors. They simplify the interconnections. Interconnection patterns that perform basic logic gates are stored in a library, which can then be used to customize rows of uncommitted ...