電氣電子專業(yè)外文翻譯at89c51單片機(jī)的介紹-單片機(jī)-免費(fèi)閱讀
【正文】 閑散和掉電模式外部引腳狀態(tài)。此時(shí)，片內(nèi)隨機(jī)存取數(shù)據(jù)存儲(chǔ)器和所有特殊功能寄存器的內(nèi)容保持不變。由于外部時(shí)鐘信號(hào)是通過(guò)一個(gè) 2 分頻觸發(fā)器后作為內(nèi)部時(shí)鐘信號(hào)的，所以對(duì)外部時(shí)鐘信號(hào)的占空比沒(méi)有特殊要求，但最小高電平持續(xù)時(shí)間和最大的低電平持續(xù)時(shí)間應(yīng)符合產(chǎn)品技術(shù)條件的要求。 外接石英晶體及電容 C1， C2 接在放大器的反饋回路中構(gòu)成并聯(lián)震蕩電路。欲使中央處理器僅訪問(wèn)外部程序存儲(chǔ)器， EA 端必須保持低電平。即使不訪問(wèn)外部存儲(chǔ)器， ALE 以時(shí)鐘震蕩頻率的 1/16 輸出固定的正脈沖信號(hào)，因此它可對(duì)輸出時(shí)鐘或用于定時(shí)目的。閃爍編程或校驗(yàn)時(shí)， P2 口接收高位地址和其它控制信號(hào)。對(duì)端口寫 “1”，通過(guò)內(nèi)部的電阻把端口拉到高電平，此時(shí)可作為輸入口。閑散方式停止中央處理器的工作，能夠允許隨機(jī)存取數(shù)據(jù)存儲(chǔ)器、定時(shí) /計(jì)數(shù)器、串行通信口及中斷系統(tǒng)繼續(xù)工作。外文翻譯 9 原文： The Introduction of AT89C51 Description The AT89C51 is a lowpower, highperformance CMOS 8bit microputer with 4K bytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel’s highdensity nonvolatile memory technology and is patible with the industrystandard MCS51 instruction set and pinout. The onchip Flash allows the program memory to be reprogrammed insystem or by a conventional nonvolatile memory programmer. By bining a versatile 8bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microputer which provides a highlyflexible and costeffective solution to many embedded control applications. Function characteristic The AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16bit timer/counters, a five vector twolevel interrupt architecture, a full duplex serial port, onchip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The Powerdown Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset. Pin Description VCC： Supply voltage. GND： Ground. 10 Port 0 Port 0 is an 8bit opendrain bidirectional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as highimpedance 0 may also be configured to be the multiplexed loworder address/data bus during accesses to external program and data memory. In this mode P0 has internal 0 also receives the code bytes during Flash programming,and outputs the code bytes during programverification. External pullups are required during programverification. Port 1 Port 1 is an 8bit bidirectional I/O port with internal Por
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