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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In real full-custom layout in which the geometry, orientation and placement of every transistor is done individually by qnd designer, design productivity is usually very low – typically 10 to 20 transistors per day, per designer.

Here, the numbers for circuit complexity should be interpreted only as representative examples to show the order-of-magnitude. If you don’t obey hierarchy rules, a few things may not work modulzrity in general you’ll just get a messy, difficult to debug, difficult to explain system. Sophisticated computer-aided design CAD tools and methodologies are developed and applied in order to manage the rapidly increasing design complexity.

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. Notice that the nMOS transistors are located closer to the ground rail while the pMOS transistors are placed closer to the power rail.

All of the blocks can be combined with ease at the end of the design process, to form the large system. If all taps lie along the power rails at the top and bottom of the cells, we can use explicit PIMPLANT to ensure that there are no errors where cells meet. Regardless of the actual size of the project, the basic principles of structured design will improve the prospects of success. In the case of layout, the leaf mdularity i.


Hierarchy Rules for Layout

In the case of layout, the interface is defined by the ports of the sub-modules which must be at specified locations and using specified conductors. Although regulqrity design flow provides an excellent design process control, in reality, there is no truly unidirectional top-down design flow. The electronics industry has achieved a phenomenal growth over the last two decades, mainly due to the rapid advances in integration technologies, large-scale systems design – in short, due to the advent of VLSI.

At lower levels of the physical hierarchy, the internal mask.

Hierarchy Rules for Layout

As an example of structural hierarchy, Fig. The level of integration as measured by the number of logic gates in a monolithic chip has been steadily rising for almost three decades, mainly due to the rapid progress in processing technology and interconnect technology.

In this way, we hide information in an attempt to reduce the apparent complexity of a module. 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. Since the same layout design is replicated, there would not be any alternative to high density memory chip design.

Some full custom chips can be also implemented exclusively with standard cells. The strategy is one of Divide and Conquer. The standard cell is also called the polycell.

Design of VLSI Systems – Chapter 1

In most cases, full utilization of the FPGA chip area is not possible – many cell sites may remain unused. For intercell routing, however, some of the uncommitted transistors must be sacrificed.


The monolithic integration of a large number of functions on a single chip usually provides:. Your work with magic will not require explicit keep out masks, but you will be required to observe implied keep out areas as appropriate. Black Box or Abstract View The following figure shows the ports defined earlier together with explicit Metal1 and Metal2 keep out areas which ensure locslity no unwanted interaction takes place.

Magic will not enforce hierarchy rules. The characterization of each cell is done for several different categories. Notice that within the cell block, the separations between neighboring rows depend on the number of wires in the routing channel between the cell rows.

The control terminals of multiplexers are not shown explicitly in Fig. To enable automated placement of the cells and routing of inter-cell connections, each cell layout is designed with a fixed height, so that a number of cells can be abutted side-by-side to form rows.

The typical design flow of an FPGA chip starts with the behavioral description of its functionality, using a hardware description language such as VHDL. Significant benefits acrue where modules may be re-used regulsrity a system design. One of the most important characteristics of information services is their increasing need for very high processing power and bandwidth in order to handle real-time video, for example.

At this lower level of the hierarchy, the design of a simple circuit realizing a well-defined Boolean function is much more easier to handle than at the higher levels of the hierarchy.