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Whenever the word microprocessor is referred, it conjures up a picture of a desktop or laptop computer running an application such as a word processor or a spreadsheet. While this is a common application for microprocessors, it is not the only one and the fact is most people use them indirectly in common objects and consumer electronics without realising it. Without the microprocessor, these products would not be as sophisticated or cheap as they are today. The embedding of microprocessors into equipment and mobile devices started before the appearance of the personal computer and consumes the majority of microprocessors that are made today. In this way, embedded microprocessors are more deeply ingrained into everyday life than any other electronic circuit that is made. A large car may have over 50 microprocessors controlling functions such as the engine through engine management systems, brakes with electronic anti-lock brakes, transmission with traction control and electronically controlled gearboxes, safety with airbag systems, electric windows, air-conditioning and so on. With a well-equipped car, nearly every aspect has some form of electronic control associated with it and thus a need for a microprocessor within an embedded system.
A washing machine may have a common microcontroller that contains the different washing programs, provides the power control for the various motors and pumps and even controls the display that tells you how the wash cycles are proceeding. Mobile phones contain more processing power than a desktop processor of a few years ago. Many gadgets contain microprocessors and there are even kitchen appliances such as bread machines that use microcontroller-based control systems. The word control is very apt for embedded systems because in virtually every embedded system application, the goal is to control an aspect of a physical system such as temperature, motion, and so on using a variety of inputs. With the recent advent of the digital age replacing many of the analogue technologies in the consumer world, the dominance of the embedded system is ever greater. Each digital consumer device such as a digital camera, DVD or MP3 player all depend on an embedded system to realise the system. As a result, the skills behind embedded systems design are as diverse as the systems that have been built although they share a common heritage.
There are many definitions for this but the best way to define it is to describe it in terms of what it is not and with examples of how it is used.
An embedded system is a microcontroller-based system that is built to control a function or range of functions and is not designed to be programmed by the end user in the same way that a PC is. Yes, a user can make choices concerning functionality but cannot change the functionality of the system by adding/replacing software. With a PC, this is exactly what a user can do: one minute the PC is a word processor and the next it’s a games machine simply by changing the software. An embedded system is designed to perform one particular task albeit with choices and different options. The last point is important because it differentiates itself from the world of the PC where the end user does reprogram it whenever a different software package is bought and run. However, PCs have provided an easily accessible source of hardware and software for embedded systems and it should be no surprise that they form the basis of many embedded systems. To reflect this, there are many popular microcontroller projects to build a simple hobby gadget or a sophisticated data logging system for a race car.
If this need to control the physical world is so great, what is so special about embedded systems that has led to the widespread use of microprocessors? There are several major reasons and these have accumulated over the years as the technology has progressed and developed.
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Tags: Embedded System
Posted in Hardware · August 24th, 2010 · Comments (0)
Field-Programmable Gate Arrays are pre-fabricated silicon devices that can be electrically programmed to become almost any kind of digital circuit or system. They provide a number of compelling advantages over fixed-function Application Specific Integrated Circuit (ASIC) technologies such as standard cells: ASICs typically take months to fabricate and cost hundreds of thousands to millions of dollars to obtain the first device; FPGAs are configured in less than a second (and can often be reconfigured if a mistake is made) and cost anywhere from a few dollars to a few thousand dollars. The flexible nature of an FPGA comes at a significant cost in area, delay, and power consumption: an FPGA needs approximately 20 to 35 times more area than a standard cell ASIC, has a speed performance roughly 3 to 4 times slower than an ASIC and consumes roughly 10 times as much dynamic power. These disadvantages arise largely from an FPGA’s programmable routing fabric which trades area, speed, and power in return for “instant” fabrication.
Despite these disadvantages, FPGAs present a strong alternative for digital system implementation based on their fast-turnaround and low volume cost. For small enterprises or small entities within large corporations, FPGAs provide the only economical access to the scalability and performance provided by Moore’s law. As Moore’s law progresses, the ensuing difficulties brought about by state-of-the-art deep submicron processes make ASIC design more difficult and expensive. The investment required to produce a useful ASIC consists of several very large items in terms of time and money:
(1) State-of-the-art ASIC CAD tools for synthesis, placement, routing, extraction, simulation, timing analysis, and power analysis are extremely costly.
(2) The mask costs of a fully-fabricated device can be millions of dollars. This cost can be reduced if prototyping costs are shared among different, smaller ASICs, or if a “structured ASIC” approach, which requires fewer masks, is used.
(3) The loaded cost of an engineering team required to develop a large ASIC over multiple years is huge. (This cost would be related, but smaller for an FPGA design team.)
These high costs, and the need for a proportionally higher return on investment, drive most digital design starts toward Field-Programmable Gate Array implementation.
The two essential technologies which distinguish FPGAs are architecture and the computer-aided design (CAD) tools that a user must employ to create FPGA designs. The goal of the industry is to examine the existing state of the art in FPGA architecture and to project future trends.
While the continued scaling of CMOS gives rise to problems, the increased integration both allows and forces architects to consider new architectures for FPGAs. Embedded industry examines alternative architectures for FPGAs that are enabled by or necessitated by the continued improvements in process technology, along with new ideas and directions that have recently been proposed to simply achieve better performance, computational density, and power consumption.
This article has explored some basic issues in the complex and rapidly evolving world of pre-fabricated FPGA architectures. While these devices have changed dramatically in last two decades, it is clear that many essential questions remain, driven by rapid changes in technology and applications.
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Tags: fpga
Posted in Hardware · June 10th, 2010 · Comments (0)