【文章內(nèi)容簡(jiǎn)介】 止。需要注意的是，當(dāng)由硬件復(fù)位來(lái)終止空閑工作模式時(shí)，CPU 通常是從激活空閑模式那條指令的下一條指令開(kāi)始繼續(xù)執(zhí)行程序的，要完成內(nèi)部復(fù)位操作，硬件復(fù)位脈沖要保持兩個(gè)機(jī)器周期（24個(gè)時(shí)鐘周期）有效，在這種情況下，內(nèi)部禁止CPU訪問(wèn)片內(nèi)RAM，而允許訪問(wèn)其它端口。為了避免可能對(duì)端口產(chǎn)生意外寫入，激活空閑模式的那條指令后一條指令不應(yīng)是一條對(duì)端口或外部存儲(chǔ)器的寫入指令。掉電模式：在掉電模式下，振蕩器停止工作，進(jìn)入掉電模式的指令是最后一條被執(zhí)行的指令，片內(nèi)RAM 和特殊功能寄存器的內(nèi)容在終止掉電模式前被凍結(jié)。退出掉電模式的唯一方法是硬件復(fù)位，復(fù)位后將重新定義全部特殊功能寄存器但不改變RAM中的內(nèi)容，在Vcc恢復(fù)到正常工作電平前，復(fù)位應(yīng)無(wú)效，且必須保持一定時(shí)間以使振蕩器重啟動(dòng)并穩(wěn)定工作。程序存儲(chǔ)器的加密：AT89C51 可使用對(duì)芯片上的3 個(gè)加密位LBLBLB3 進(jìn)行編程（P）或不編程（U）來(lái)得到如下表所示的功能加密位保護(hù)功能表：當(dāng)加密位LB1 被編程時(shí)，在復(fù)位期間，EA端的邏輯電平被采樣并鎖存，如果單片機(jī)上電后一直沒(méi)有復(fù)位，則鎖存起的初始值是一個(gè)隨機(jī)數(shù)，且這個(gè)隨機(jī)數(shù)會(huì)一直保存到真正復(fù)位為止。為使單片機(jī)能正常工作，被鎖存的EA 電平值必須與該引腳當(dāng)前的邏輯電平一致。此外，加密位只能通過(guò)整片擦除的方法清除。Flash閃速存儲(chǔ)器的編程：AT89C51 單片機(jī)內(nèi)部有4k 字節(jié)的Flash PEROM，這個(gè)Flash 存儲(chǔ)陣列出廠時(shí)已處于擦除狀態(tài)（即所有存儲(chǔ)單元的內(nèi)容均為FFH），用戶隨時(shí)可對(duì)其進(jìn)行編程。編程接口可接收高電壓（+12V）或低電壓（Vcc）的允許編程信號(hào)。低電壓編程模式適合于用戶在線編程系統(tǒng)，而高電壓編程模式可與通用EPROM編程器兼容。AT89C51單片機(jī)中，有些屬于低電壓編程方式，而有些則是高電壓編程方式，用戶可從芯片上的型號(hào)和讀取芯片內(nèi)的名字節(jié)獲得該信息。AT89C51的程序存儲(chǔ)器陣列是采用字節(jié)寫入方式編程的，每次寫入一個(gè)字節(jié)，要對(duì)整個(gè)芯片內(nèi)的PEROM程序存儲(chǔ)器寫入一個(gè)非空字節(jié)，必須使用片擦除的方式將整個(gè)存儲(chǔ)器的內(nèi)容清除。核準(zhǔn)通過(guò)，歸檔資料。未經(jīng)允許，請(qǐng)勿外傳！9JWKffwvGtYM*Jgamp。6a*CZ7H$dq8KqqfHVZFedswSyXTyamp。QA9wkxFyeQ^!djsXuyUP2kNXpRWXmAamp。UE9aQ@Gn8xp$Ramp。849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5ux^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmUE9aQ@Gn8xp$Ramp。849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5ux^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z8vGtYM*Jgamp。6a*CZ7H$dq8KqqfHVZFedswSyXTyamp。QA9wkxFyeQ^!djsXuyUP2kNXpRWXmAamp。UE9aQ@Gn8xp$Ramp。849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^G89AmUE9aQ@Gn8xp$Ramp。849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5ux^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z8vGtYM*Jgamp。6a*CZ7H$dq8KqqfHVZFedswSyXTyamp。QA9wkxFyeQ^!djsXuyUP2kNXpRWXmAamp。UE9aQ@Gn8xp$Ramp。849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5ux^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmUE9aQ@Gn8xp$Ramp。849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5ux^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5ux^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$U*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89Amv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5ux^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$U*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz84!z89Amv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5ux^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$UE9wEwZQc@UE%amp。qYp@Eh5pDx2zVkumamp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9CpbK!zn%Mz849Gx^Gjqv^$U*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRrWwc^vR9amp。gTXRm6X4NGpP$vSTTamp。ksv*3tnGK8!z89AmYWpazadNuKNamp。MuWFA5uxY7JnD6YWRr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