【正文】 特殊功能寄存器 復 位 值 特殊功能寄存器 復 位 值PC 0000H TMOD 00HACC 00H TCON 00HB 00H TH0 00HPSW 00H TL0 00HSP 07H TH1 00HDPTR 0000H TL1 00HP0～P3 FFH SCON 00HIP XXX0 0000B SBUF XXXX XXXXBIE 0XX0 0000B PCON 0XXX 0000B注：PC 稱為程序指針，它被用來存儲下一條要執(zhí)行的指令地址，PC 的位置并不在特殊功能存儲器區(qū)域。圖 所示復位電路由 C1 和 R1 組成。在這個放大電路的對外引腳 XTAL2（引腳 18）和 XTAL1（引腳19）接上晶體和電容就可以構(gòu)成單片機的時鐘電路。CPU 通過向相應的外部數(shù)據(jù)存儲器地址單元寫入數(shù)據(jù)實現(xiàn)控制對應的片外外圍器件的工作，從相應的外部數(shù)據(jù)存儲器地址單元讀出數(shù)據(jù)實現(xiàn)讀取對應的片外外圍器件的工作結(jié)果。如果向這些存儲單元寫入數(shù)據(jù)將產(chǎn)生不確定的效果，從它們讀取數(shù)據(jù)將得到一個隨機數(shù)。表 工作寄存器地址映射表0 組（RS1=0，RS0=0）1 組（RS1=0，RS0=1）2 組（RS1=1，RS0=0）3 組（RS1=1，RS0=1）地址寄存器地址寄存器地址寄存器地址寄存器00H R0 08H R0 10H R0 18H R001H R1 09H R1 11H R1 19H R102H R2 0AH R2 12H R2 1AH R203H R3 0BH R3 13H R3 1BH R304H R4 0CH R4 14H R4 1CH R405H R5 0DH R5 15H R5 1DH R506H R6 0EH R6 16H R6 1EH R607H R7 0FH R7 17H R7 1FH R7表 字節(jié)地址與位地址的關(guān)系位 地 址字節(jié)地址 D7 D6 D5 D4 D3 D2 D1 D02FH 7F 7E 7D 7C 7B 7A 79 782EH 77 76 75 74 73 72 71 702DH 6F 6E 6D 6C 6B 6A 69 682CH 67 66 65 64 63 62 61 602BH 5F 5E 5D 5C 5B 5A 59 582AH 57 56 55 54 53 52 51 5029H 4F 4E 4D 4C 4B 4A 49 4828H 47 46 45 44 43 42 41 4027H 3F 3E 3D 3C 3B 3A 39 3826H 37 36 35 34 33 32 31 3025H 2F 2E 2D 2C 2B 2A 29 2824H 27 26 25 24 23 22 21 2023H 1F 1E 1D 1C 1B 1A 19 1822H 17 16 15 14 13 12 11 1021H 0F 0E 0D 0C 0B 0A 09 08720H 07 06 05 04 03 02 01 00在工作寄存器區(qū)上面，內(nèi)部數(shù)據(jù)存儲器的地址從 20H～2FH 的 16 個字節(jié)范圍內(nèi)，既可以通過字節(jié)尋址的方式進入，也可以通過位尋址的方式進入，位地址范圍從 00H到 7FH。它可以進一步被分為 3 部分，如圖 所示。高于 0FFFH 的程序存儲空間只能被映射為外部程序存儲器。上述存儲空間在物理上可以被映射到 4 個區(qū)域：片內(nèi)程序存儲器和片外程序存儲器，片內(nèi)數(shù)據(jù)存儲器和片外數(shù)據(jù)存儲器。諸如定時自動報警、按時自動打鈴、時間程序自動控制、定時廣播、定時啟閉電路、定時開關(guān)烘箱、通斷動力設備，甚至各種定時電氣的自動啟用等，所有這些，都是以鐘表數(shù)字化為基礎的。但是，一旦重要事情，一時的2耽誤可能釀成大禍。MCS51 系列單片機優(yōu)異的性能 /價格比使得它從面世以來就獲得用戶的認可。關(guān)鍵詞：單片機技術(shù)，AT89S51，液晶驅(qū)動，電子鬧鐘IIIABSTRACTBecause of its extremely high performanceprice ratio, the singlechip puter (SCC) has been paid great attention to ever since it came out in 1970s of 20th Century, and has gained an extensive applicable field and fast development. Among all kinds of SCCs, 51 SCC is the most typical and representative one. This design, adopting AT89S51 chip as the core part with some necessary peripheral circuits, is a simple electronic clock which uses 5V DC as the power supply. In hardware aspect, besides the CPU, six sevensegment LED digitubes are used for display, which work in a dynamically scanning display mode and driven by 74SL14 chip. The LEDs can accurately indicate hour and minute and two buttons can be used to adjust the time. While in the software aspect, the programming language is assembly language. The whole electronic clock system has functions of time display, adjustment, bellsetting and reset, etc. Choose the smallest SCM system applications,add Comparison procedures, time to adjust procedures and faint buzzing procedures, Through relatively faint buzzing trigger procedures to achieve alarm clock function, Completed the design needs of the software environment. Keil introduced and the use of SCM software simulation debugging, testing the feasibility. Keywords: technology of the onechip puter，AT89S51，the liquid crystal is driven，Electronic alarm clockIV目 錄第 1 章 緒 論 ......................................................................................................................1 單片機簡介 ................................................................................................................1 電子鬧鐘的重要意義 ................................................................................................1 本文的主要工作 ........................................................................................................2第 2 章 AT89S51 單片機的硬件系統(tǒng) ............................................................................3 AT89S51 單片機的特性 .............................................................................................3 AT89S51 單片機的封裝 ...........................................................................................3 存儲空間 ....................................................................................................................3 程序存儲空間 ..................................................................................................4 數(shù)據(jù)存儲空間 ..................................................................................................5 單片機最小應用系統(tǒng)電路 ........................................................................................8 供電電路 .............................................................................................................8 程序存儲器選擇電路 .....................................................................................