【導(dǎo)讀】清楚，符合漢語習(xí)慣，態(tài)度端正，表現(xiàn)練好。準(zhǔn)MCS-5l指令系統(tǒng)，片內(nèi)置通用8位中央處理器和Flash存儲(chǔ)單元，功能強(qiáng)大。AT89C2051單片機(jī)可為您提供許多高性價(jià)比的應(yīng)用場合。AT89C2051提供以下標(biāo)準(zhǔn)功能：2k字節(jié)Flash閃速存儲(chǔ)器，128字節(jié)內(nèi)部RAM，至0HZ的靜態(tài)邏輯操作，并支持兩種軟件可選的節(jié)電工作模式。的工作，但允許RAM，定時(shí)／計(jì)數(shù)器，串行通信口及中斷系統(tǒng)繼續(xù)工作。作為輸出口用時(shí)，每位能吸收電流的方式驅(qū)動(dòng)8個(gè)TTL邏輯門電路，對(duì)端口。在訪問外部數(shù)據(jù)存儲(chǔ)器或程序存儲(chǔ)器時(shí)，這組口。作輸入口使用時(shí)，因?yàn)閮?nèi)部存在上拉電阻，F(xiàn)Iash編程和程序校驗(yàn)期間，平將使單片機(jī)復(fù)位。此外，該引腳會(huì)被微弱拉高，單片機(jī)執(zhí)行外部程序時(shí)，在此期間，當(dāng)訪問外部數(shù)據(jù)存儲(chǔ)器，這兩次有效的PSEN信號(hào)出現(xiàn)。復(fù)位時(shí)內(nèi)部會(huì)鎖存EA端狀態(tài)。和XTAL2分別是該放大器的輸入端和輸出端。陶瓷諧振器）及電容C1、C2接在放大器的反饋回路中構(gòu)成并聯(lián)振蕩電路。薦電容使用30pF±10pF，而如使用陶瓷諧振器建議選擇40pF±10F。

　　

【正文】 l at that pin in order for the device to function properly. Programming the Flash The AT89C2051 is normally shipped with the onchip Flash memory array in the erased state (that is, contents = FFH) and ready to be programmed. The programming interface accepts either a highvoltage (12volt) or a lowvoltage (VCC) program enable signal. The lowvoltage programming mode provides a convenient way to program the AT89C2051 inside the user’s system, while the highvoltage programming mode is patible with conventional thirdparty Flash or EPROM programmers. The AT89C2051 is shipped with either the highvoltage or lowvoltage programming mode enabled. The respective topside marking and device signature codes are listed in the following table. The AT89C2051 code memory array is programmed bytebybyte in either programming mode. To program any nonblank byte in the onchip Flash Memory, the entire memory must be erased using the Chip Erase Mode. Programming Algorithm: Before programming the AT89C2051, the address, data and control signals should be set up according to the Flash programming mode table and Figure 3 and Figure 4. To program the AT89C2051, take the following steps. 1. Input the desired memory location on the address lines. 2. Input the appropriate data byte on the data lines. 3. Activate the correct bination of control signals. 4. Raise EA/VPP to 12V for the highvoltage programming mode. 5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The bytewrite cycle is selftimed and typically takes no more than steps 1 through 5, changing the address and data for the entire array or until the end of the object file is reached. Data Polling: The AT89C2051 features Data Polling to indicate the end of a write cycle. During a write cycle, an attempted read of the last byte written will result in the plement of the written datum on . Once the write cycle has been pleted, true data are valid on all outputs, and the next cycle may begin. Data Polling may begin any time after a write cycle has been initiated. Ready/Busy: The progress of byte programming can also be monitored by the RDY/BSY output signal. is pulled low after ALE goes high during programming to indicate BUSY. is pulled high again when programming is done to indicate READY. Program Verify: If lock bits LB1 and LB2 have not been programmed, the programmed code data can be read back via the address and data lines for verification. The lock bits cannot be verified directly. Verification of the lock bits is achieved by observing that their features are enabled. Chip Erase: The entire Flash array is erased electrically by using the proper bination of control signals and by holding ALE/PROG low for 10 ms. The code array is written with all “1”s. The chip erase operation must be executed before the code memory can be reprogrammed. Reading the Signature Bytes: The signature bytes are read by the same procedure as a normal verification of locations 030H, 031H, and 032H, except that and must be pulled to a logic low. The values returned are as follows. (030H) = 1EH indicates manufactured by Atmel (031H) = 51H indicates 89C2051 (032H) = FFH indicates 12V programming (032H) = 05H indicates 5V programming Programming Interface Every code byte in the Flash array can be written and the entire array can be erased by using the appropriate bination of control signals. The write operation cycle is selftimed and once initiated, will automatically time itself to pletion. All major programming vendors offer worldwide support for the Atmel microcontroller series. Please contact your local programming vendor for the appropriate software revision. Programming and Verifying the Flash Memory