【正文】 s budget over 25%.Most microcontrollers at this time had two variants. One had an erasable EPROM program memory, which was significantly more expensive than the PROM variant which was only programmable once. Erasing the EPROM required exposure to ultraviolet light through a transparent quartz lid. Onetime parts could be made in lowercost opaque plastic packages.In 1993, the introduction of EEPROM memory allowed microcontrollers (beginning with the Microchip PIC16x84) to be electrically erased quickly without an expensive package as required for EPROM, allowing both rapid prototyping, and In System Programming. The same year, Atmel introduced the first microcontroller using Flash memory. Other panies rapidly followed suit, with both memory types.Cost has plummeted over time, with the cheapest 8bit microcontrollers being available for under $ in quantity (thousands) in 2009, and some 32bit microcontrollers around $1 for similar quantities.Nowadays microcontrollers are cheap and readily available for hobbyists, with large online munities around certain processors.In the future, MRAM could potentially be used in microcontrollers as it has infinite endurance and its incremental semiconductor wafer process cost is relatively low.VolumesAbout 55% of all CPUs sold in the world are 8bit microcontrollers and microprocessors. According to Semico, over four billion 8bit microcontrollers were sold in 2006.A typical home in a developed country is likely to have only four generalpurpose microprocessors but around three dozen microcontrollers. A typical midrange automobile has as many as 30 or more microcontrollers. They can also be found in many electrical devices such as washing machines, microwave ovens, and telephones.Embedded designA microcontroller can be considered a selfcontained system with a processor, memory and peripherals and can be used as an embedded system.[1] The majority of microcontrollers in use today are embedded in other machinery, such as automobiles, telephones, appliances, and peripherals for puter systems. These are called embedded systems. While some embedded systems are very sophisticated, many have minimal requirements for memory and program length, with no operating system, and low software plexity. Typical input and output devices include switches, relays, solenoids, LEDs, small or custom LCD displays, radio frequency devices, and sensors for data such as temperature, humidity, light level etc. Embedded systems usually have no keyboard, screen, disks, printers, or other recognizable I/O devices of a personal puter, and may lack human interaction devices of any kind.InterruptsMicrocontrollers must provide real time (predictable, though not necessarily fast) response to events in the embedded system they are controlling. When certain events occur, an interrupt system can signal the processor to suspend processing the current instruction sequence and to begin an interrupt service routine (ISR, or interrupt handler). The ISR will perform any processing required based on the source of the interrupt before returning to the original instruction sequence. Possible interrupt sources are device dependent, and often include events such as an internal timer overflow, pleting an analog to digital conversion, a logic level change on an input such as from a button being pressed, and data received on a munication link. Where power consumption is important as in battery operated devices, interrupts may also wake a microcontroller from a low power sleep state where the processor is halted until required to do something by a peripheral event.[ProgramsMicrocontroller programs must fit in the available onchip program memory, since it would be costly to provide a system with external, expandable, memory. Compilers and assemblers are used to convert highlevel language and assembler language codes into a pact machine code for storage in the microcontroller39。s President, Luke J. Valenter, stated that the microcontroller was one of the most successful in the pany39。C, uC or MCU) is a small puter on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal puters or other general purpose applications.Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, and toys. By reducing the size and cost pared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to digitally control even more devices and processes. Mixed signal microcontrollers are mon, integrating analog ponents needed to control nondigital electronic systems.Some microcontrollers may use Fourbit words and operate at clock rate frequencies as low as 4 kHz, for low power consumption (milliwatts or microwatts). They will generally have the ability to retain functionality while waiting for an event such as a button press or other interrupt。第二版。傳感器原理及應(yīng)用[M]北京航空航天大學(xué)出版社,2004.[5][6]陳杰，：高等教育出版社，2002.[7][M]北京：清華大學(xué)出版社，2005.[8]：電子工業(yè)出版社，2009.[9]吳麒，王詩(shī)宓。參考文獻(xiàn)[1]宋瑞,何世偉. 城市交通系統(tǒng)可持續(xù)發(fā)展問(wèn)題的研究 [J]. 北方交通大學(xué)學(xué)報(bào),1999, 23(5): 711[2]翼紅舉，基于ARM的停車場(chǎng)管理系統(tǒng)[J]。除此之外，老師也一直對(duì)我的設(shè)計(jì)方法與論文的撰寫提出思想和意見，并對(duì)設(shè)計(jì)中所出現(xiàn)的問(wèn)題認(rèn)真負(fù)責(zé)指導(dǎo)，使我的畢業(yè)設(shè)計(jì)課題更加完善，也使我接觸到了許多有益的思考也獲取了許多新的理論知識(shí)。逐步有了設(shè)計(jì)的思想，在此過(guò)程中遇到了許許多多棘手的問(wèn)題，但最終都逐一解決了。 致謝 這次畢業(yè)設(shè)計(jì)是大學(xué)階段的最后一次設(shè)計(jì)，持續(xù)的時(shí)間也比較長(zhǎng)，從去年的十一月份的選題到今天完成論文稿有半年時(shí)間，在這半年的時(shí)間里，自己學(xué)到了很多平時(shí)課程學(xué)中沒(méi)有涉及的知識(shí)與設(shè)計(jì)思想。 （2）可靠性：系統(tǒng)利用串口監(jiān)控記錄車流量，能很好的克服傳統(tǒng)計(jì)數(shù)方式的缺陷。 隨著電子設(shè)計(jì)自動(dòng)化技術(shù)的發(fā)展，像這種基于課程邏輯器件的系統(tǒng)設(shè)計(jì)的完整方案將會(huì)越來(lái)越受人們重視。但是此系統(tǒng)的完善性還有待提高。該系統(tǒng)所實(shí)現(xiàn)的功能及性能可以經(jīng)過(guò)適當(dāng)?shù)脑O(shè)計(jì)和完善運(yùn)用與生活和生產(chǎn)實(shí)際中，例如一些擁擠的馬路，可以使用本方案來(lái)解決。 結(jié)論 道路車流