【正文】 ptionThe AT89S52 is a lowpower, highperformance CMOS 8bit microcontroller with 8Kbytes of insystem programmable Flash memory. The device is manufactured usingAtmel’s highdensity nonvolatile memory technology and is patible with the industrystandard 80C51 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 insystem programmable Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which provides a highlyflexible and costeffective solution to many embedded control applications.The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytesof RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16bit timer/counters, a sixvector twolevel interrupt architecture, a full duplex serial port, onchip oscillator, and clock circuitry. In addition, the AT89S52 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 interruptor hardware reset.Pin DescriptionVCCSupply voltage.GNDGround.Port 0Port 0 is an 8bit open drain 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 inputs. Port 0 can also be configured to be the multiplexed loworder address/data bus during accesses to external programand data memory. In this mode, P0 has internalpullups.Port 0 also receives the code bytes during Flash programming and outputs the code bytes during program verification. External pullups are required during program verification.Port 1Port 1 is an 8bit bidirectional I/O port with internal Port 1 output buffers can sink/source four TTL 1s are written to Port 1 pins, they are pulled high bythe internal pullups and can be used as inputs. As inputs,Port 1 pins that are externally being pulled low will sourcecurrent (IIL) because of the internal pullups. In addition, and can be configured to be thetimer/counter 2 external count input () and thetimer/counter 2 trigger input (), respectively, asshown in the following 1 also receives the loworder address bytes duringFlash programming and verification.Port 2Port 2 is an 8bit bidirectional I/O port with internal Port 2 output buffers can sink/source four TTL 1s are written to Port 2 pins, they are pulled high bythe internal pullups and can be used as inputs. As inputs,Port 2 pins that are externally being pulled low will sourcecurrent (IIL) because of the internal pullups.Port 2 emits the highorder address byte during fetches from external program memory and during accesses to external data memory that use 16bit addresses (MOVX DPTR). In this application, Port 2 uses strong internal pullups when emitting 1s. During accesses to external data memory that use 8bit addresses (MOVX RI), Port 2 emits the contents of the P2 Special Function Register.Port 2 also receives the highorder address bits and some control signals during Flash programming and verification.Port 3Port 3 is an 8bit bidirectional I/O port with internal Port 3 output buffers can sink/source four TTL 1s are written to Port 3 pins, they are pulled high by the internal pullups and can be used as inputs. As inputs,Port 3 pins that are externally being pulled low will source current (IIL) because of the 3 also serves the functions of various special features of the AT89S52, as shown in the following table. Port 3 also receives some control signals for Flash programming and verification.RSTReset input. A high on this pin for two machine cycles while the oscillator is running resets the device. This pin drives High for 96 oscillator periods after the Watchdog times DISRTO bit in SFR AUXR (address 8EH) can be used to disable this feature. In the default state of bit DISRTO,the RESET HIGH out feature is enabled.ALE/PROGAddress Latch Enable (ALE) is an output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG)during Flash programming. In normal operation, ALE is emitted at a constant rate of1/6the oscillator frequency and may be used for external timing or clocking purposes. Note, however, that one ALEpulse is skipped during each access to external data memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALEdisable bit has no effec。 count_hour++。 count_second++。老師博學(xué)多才、實(shí)踐經(jīng)驗(yàn)豐富以及認(rèn)真嚴(yán)謹(jǐn)?shù)膽B(tài)度深深的吸引了我，讓我更加努力去解決遇到的難題。參考文獻(xiàn)[1] 高吉祥. 電子技術(shù)基礎(chǔ)實(shí)驗(yàn)與課程設(shè)計(jì)[M], 2002[2] 陳桂友，柴遠(yuǎn)斌. 單片機(jī)運(yùn)用技術(shù)[M] .機(jī)械工業(yè)出版社，2008[3] 謝自美. 電子線路設(shè)計(jì)、實(shí)驗(yàn)、測(cè)試[M], 2003[4] 馬忠梅. 單片機(jī)的C語(yǔ)言應(yīng)用程序設(shè)計(jì)[M] .北京：航空航天大學(xué)出版社，1999[5] 呂思忠. 數(shù)字電路實(shí)驗(yàn)與課程設(shè)計(jì)[M], 2001 [6] ，提高，開(kāi)發(fā)，拓展全攻略[M] .北京：電子工業(yè)出版社，2009[7] 焦素敏. 數(shù)字電子技術(shù)基礎(chǔ)[M], 2005 [8] 林立，張俊亮. 單片機(jī)原理及應(yīng)用：基于Proteus和Keil c（第二版）[M] .電子工業(yè)出版社, 2002[9] 馬斌，韓忠華，王長(zhǎng)濤. 單片機(jī)原理及應(yīng)用C語(yǔ)言程序設(shè)計(jì)與實(shí)現(xiàn) [M]. 北京：人民郵電出版社，2009[10] 彭小軍. 用單片機(jī)實(shí)現(xiàn)電子時(shí)鐘 [J]. 新余高專學(xué)報(bào)，2004，9[11] 胡長(zhǎng)勝. 單片機(jī)及應(yīng)用 [M]. 北京：高等教育出版社，2006[12] 朱宇光. 單片機(jī)應(yīng)用新技術(shù)教程 [M]. 北京：電子工業(yè)出版社，2000[13] 譚浩強(qiáng)．C程序設(shè)計(jì)（第4版） [M]．北京：清華大學(xué)出版社，2012，7[14] 明日科技．C語(yǔ)言從入門到精通（實(shí)例版）[M]．清華大學(xué)出版社， 2012，9[15] 郭天祥．新概念51單片機(jī)C語(yǔ)言教程入門提高開(kāi)發(fā)拓展全攻略[M]．中國(guó)水利水電出版社，2009[16] 蘇小紅，李東，王甜甜．C語(yǔ)言大學(xué)教程（第6版） [M]．電子工業(yè)出版社，2012，1[17] 王浩．C語(yǔ)言標(biāo)準(zhǔn)教程 [M]．化學(xué)工業(yè)出版社，2011，1[18] 楊欣，王玉鳳．電子設(shè)計(jì)從零開(kāi)始（第2版） [M]．清華大學(xué)出版社，2010[19] 王東峰．單片機(jī)C語(yǔ)言應(yīng)用100例（第2版） [M]，電子工業(yè)出版社，2013[20] (英)高理顥 孫秀娟．Introductory Microcontroller Theory and Applications[M] ,石油大學(xué)出版社,2008[21] 韓建國(guó)，廖