【正文】 從而改變它的內(nèi)容 也 可以改變 程序 的 進行 方向 。 允許振蕩頻率為 12MHz， 每一個上述的部分 都 是通過內(nèi)部數(shù)據(jù)總線 連接 。 8051是 51 系列單芯片電腦 的 代表。倒裝芯片球柵陣列封裝（ FCBGA）始發(fā)展于 20 世紀 90 年代，這種封裝形式允許更高的引腳數(shù)。 20 世紀 80 年代， VLSI 電路的針腳超過了 DIP 封裝的應(yīng)用限制，導(dǎo)致插針網(wǎng)格陣列和 leadless chip carrier（ LCC）的出現(xiàn)。 因為 CMOS 器件只引導(dǎo)電流在邏輯門之間轉(zhuǎn)換，因而 CMOS 器件比雙級元件消耗的電流少很多。從氧化銅到鍺，再到硅，原料在 19 世紀 40 年代到 50 年代被系統(tǒng)的研究。 IC 可分為模擬 IC，數(shù)字 IC 和數(shù)?；旌?IC（同一塊 IC 上既有模擬電路也有數(shù)字電路）?？傊S著外形尺寸縮小，幾乎所有的性能指標都得到了改善 —— 單位成本 和開關(guān)功耗下降了，運行速度提高了?？梢约蛇_到一百萬個晶體管。相對于手工組裝電路使用分立的電子元器件，集成電路把大量的微晶體管集成到一個小芯片，是一個巨大的進步。 the highest density devices are thus memories。 but even a microprocessor will have memory on the chip. Although the structures are intricate – with widths which have been shrinking for decades – the layers remain much thinner than the device widths. The layers of material are fabricated much like a photographic process, although light waves in the visible spectrum cannot be used to expose a layer of material, as they would be too large for the features. Thus photons of higher frequencies (typically ultraviolet) are used to create the patterns for each layer. Because each feature is so small, electron microscopes are essential tools for a process engineer who might be debugging a fabrication process. The earliest integrated circuits were packaged in ceramic flat packs, which continued to be used by the military for their reliability and small size for many years. Commercial circuit packaging quickly moved to the dual inline package (DIP), first in ceramic and later in plastic. In the 1980s pin counts of VLSI circuits exceeded the practical limit for DIP packaging, leading to pin grid array (PGA) and leadless chip carrier (LCC) packages. Surface mount packaging appeared in the early 1980s and became popular in the late 1980s, using finer lead pitch with leads formed as either gullwing or Jlead, as exemplified by smalloutline integrated circuit a carrier which occupies an area about 30 – 50% less than an equivalent DIP, with a typical thickness that is 70% less. This package has gull wing leads protruding from the two long sides and a lead spacing of inches. 第 頁 共 頁 In the late 1990s, PQFP and TSOP packages became the most mon for high pin count devices, though PGA packages are still often used for highend microprocessors. Intel and AMD are currently transitioning from PGA packages on highend microprocessors to land grid array (LGA) packages. Ball grid array (BGA) packages have existed since the 1970s. Flipchip Ball Grid Array packages, which allow for much higher pin count than other package types, were developed in the 1990s. Most integrated circuits large enough to include identifying information include four mon sections: the manufacturer39。集成電路的大規(guī)模生產(chǎn)性，可靠性和模塊化，使得應(yīng)用標準化 IC 的電路設(shè)計迅速取代了使用離散晶體管的電路設(shè) 計。 最先進的集成電路是微處理器或稱核 ,它用于控制大到電腦小到手機或數(shù)字微波爐等。但是，納米級的 IC 并非沒有問題，其中最主要的問題是泄漏電流（參見亞閾值泄漏）。 第 頁 共 頁 數(shù)字 IC 在幾平方毫米上可以集成上百萬個邏輯門，多諧振蕩器，多路復(fù)用器和其它電路。今天，盡管元素周期表中的一些IIIV 價化合物如砷化鎵有特殊用途，如應(yīng)用于發(fā)光二極管，激光，太陽能電池和超高速集成電路，但單晶硅仍是集成電路的主流基層。隨機存取存儲器（ random access memory）是最常見的集成電路，所以密度最高的設(shè)備是存儲器，即使是微處理器上也有集成存儲器。貼片式的封裝在 20世紀 80 年代初期出現(xiàn)，在 80 年代后期開始流 行。 大多數(shù)集成電路都足夠大以包含識別信息，一般包括四個部分：制造商的名稱或標志，零件編號，生產(chǎn)批號和 /或序列號以及標識芯片制造日期的 4 位數(shù)字代碼。 一個單芯片的計算機系統(tǒng)由以下幾個部分組成：（ 1）一個 8位的 微處理器（ CPU）。其中 CPU 是一個芯片計算機的核心，它是計算機 的 指揮中心 ，是 由算術(shù)單元和控制器等部分組成 。在 8051 的單芯片電腦的電路 中 ，只需要外部石英晶體和頻率微調(diào)電容，其頻率范圍為 到 12MHz。這是一個字節(jié)的地址，其實程序計數(shù)器，