Why vlsi design flow is called a cycle

What has the author Virginia M Litwin written? What is the flow of blood within the heart known as? How is the carbon cycle realted to energy flow in ecosystems? Study Guides. Trending Questions. Still have questions? Find more answers. Previously Viewed. Unanswered Questions. What characteristics of a tragic hero does Macbeth possess and banquo lack? What could result if a 30 year old lawyer continued to eat as he did as a 17 years old football player?

What is the function of resorcinol in the seliwanoff's test? How do you maximally develop the intelligence quotient of a child? Get the Answers App. All Rights Reserved. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Answers.

From here onwards we need the help of EDA tools. RTL description is then converted to a gate-level netlist using logic synthesis tools. A gatelevel netlist is a description of the circuit in terms of gates and connections between them, which are made in such a way that they meet the timing, power and area specifications.

The Gajski-Kuhn Y-chart is a model, which captures the considerations in designing semiconductor devices. The three domains of the Gajski-Kuhn Y-chart are on radial axes.

Each of the domains can be divided into levels of abstraction, using concentric rings. Creating a structural description from a behavioral one is achieved through the processes of high-level synthesis or logical synthesis.

Although the end product is typically quite small measured in nanometers , this long journey is interesting and filled with many engineering challenges. Today, ASIC design flow is a very mature process in silicon turnkey design. To ensure successful ASIC design, engineers must follow a proven ASIC design flow which is based on a good understanding of ASIC specifications, requirements, low power design and performance, with a focus on meeting the goal of right time to market.

Two different teams are involved at this juncture:. Functional verification confirms the functionality and logical behavior of the circuit by simulation on a design entry level. This is the stage where the design team and verification team come into the cycle where they generate RTL code using test-benches.

This is known as behavioral simulation. This code coverage includes statement coverage, expression coverage, branch coverage, and toggle coverage. Thereafter, a synthesized database of the ASIC design is created in the system. When timing constraints are met with the logic synthesis, the design proceeds to the design for testability DFT techniques. Contact Us. This is the stage wherein the engineer follows the ASIC design layout requirement and specification to create its structure using EDA tools and proven methodologies.

Once all the functional blocks are implemented in the architectural document, the engineers need to brainstorm ASIC design partitioning by reusing IPs from previous projects and procuring them from other parties.

Table 1. Here, the numbers for circuit complexity should be interpreted only as representative examples to show the order-of-magnitude. A logic block can contain anywhere from 10 to transistors, depending on the function. The most important message here is that the logic complexity per chip has been and still is increasing exponentially.

The monolithic integration of a large number of functions on a single chip usually provides:. Therefore, the current trend of integration will also continue in the foreseeable future. Advances in device manufacturing technology, and especially the steady reduction of minimum feature size minimum length of a transistor or an interconnect realizable on chip support this trend.

At that time, a minimum feature size of 0. The actual development of the technology, however, has far exceeded these expectations. A minimum size of 0. As a direct result of this, the integration density has also exceeded previous expectations - the first 64 Mbit DRAM, and the INTEL Pentium microprocessor chip containing more than 3 million transistors were already available by , pushing the envelope of integration density. When comparing the integration density of integrated circuits, a clear distinction must be made between the memory chips and logic chips.

It can be observed that in terms of transistor count, logic chips contain significantly fewer transistors in any given year mainly due to large consumption of chip area for complex interconnects. Memory circuits are highly regular and thus more cells can be integrated with much less area for interconnects. Generally speaking, logic chips such as microprocessor chips and digital signal processing DSP chips contain not only large arrays of memory SRAM cells, but also many different functional units.

As a result, their design complexity is considered much higher than that of memory chips, although advanced memory chips contain some sophisticated logic functions. The design complexity of logic chips increases almost exponentially with the number of transistors to be integrated.

This is translated into the increase in the design cycle time, which is the time period from the start of the chip development until the mask-tape delivery time. However, in order to make the best use of the current technology, the chip development time has to be short enough to allow the maturing of chip manufacturing and timely delivery to customers.

As a result, the level of actual logic integration tends to fall short of the integration level achievable with the current processing technology. Sophisticated computer-aided design CAD tools and methodologies are developed and applied in order to manage the rapidly increasing design complexity.

The design process, at various levels, is usually evolutionary in nature. It starts with a given set of requirements. Initial design is developed and tested against the requirements. When requirements are not met, the design has to be improved.

If such improvement is either not possible or too costly, then the revision of requirements and its impact analysis must be considered. The Y-chart first introduced by D. Gajski shown in Fig. The design flow starts from the algorithm that describes the behavior of the target chip. The corresponding architecture of the processor is first defined.

It is mapped onto the chip surface by floorplanning. The next design evolution in the behavioral domain defines finite state machines FSMs which are structurally implemented with functional modules such as registers and arithmetic logic units ALUs. 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 third evolution starts with a behavioral module description. Individual modules are then implemented with leaf cells. The last evolution involves a detailed Boolean description of leaf cells followed by a transistor level implementation of leaf cells and mask generation. In standard-cell based design, leaf cells are already pre-designed and stored in a library for logic design use.

Note that the verification of design plays a very important role in every step during this process. The failure to properly verify a design in its early phases typically causes significant and expensive re-design at a later stage, which ultimately increases the time-to-market. Although the design process has been described in linear fashion for simplicity, in reality there are many iterations back and forth, especially between any two neighboring steps, and occasionally even remotely separated pairs.