操作系統(tǒng)精髓與設(shè)計(jì)原理英漢對照6th-資料下載頁
2025-01-08 14:54本頁面
【正文】 少（內(nèi)存）寫操作 – Leave main memory in an obsolete state使主存處于一種廢棄的狀態(tài) Roadmap – Basic Elements – Processor Registers – Instruction Execution – Interrupts – The Memory Hierarchy – Cache Memory –I/O Communication Techniques I/O TechniquesI/O通信技術(shù) ? When the processor encounters an instruction relating to I/O,當(dāng)處理器遇到一個(gè)與 I/O相關(guān)的指令時(shí) – it executes that instruction by issuing a mand to the appropriate I/O 給適當(dāng)?shù)?I/O模塊發(fā)出命令來執(zhí)行這個(gè)指令 ? Three techniques are possible for I/O operations:對 I/O操作可能有三種技術(shù)： – Programmed I/O可編程 I/O – Interruptdriven I/O中斷驅(qū)動 I/O – Direct memory access (DMA)直接內(nèi)存存取 Programmed I/O ? The I/O module performs the requested action 這個(gè) I/O模塊執(zhí)行請求動作 – then sets the appropriate bits in the I/O status register進(jìn)而設(shè)置相應(yīng)位的 I/O狀態(tài)寄存器 – but takes no further action to alert the ? As there are no interrupts, the processor must determine when the instruction is plete因?yàn)闆]有中斷，處理器必須決定指令何時(shí)完成 Programmed I/O Instruction Set指令集 ? Control控制 – Used to activate and instruct device用于激活和指示設(shè)備 ? Status狀態(tài) – Tests status conditions測試（ I/O及外圍設(shè)備）狀態(tài)條件 ? Transfer傳送 – Read/write between process register and device在處理器寄存器和外設(shè)間讀寫數(shù)據(jù) Programmed I/O Example ? Data read in a word at a time每次讀取一個(gè)字的數(shù)據(jù) – Processor remains in statuschecking look while reading當(dāng)讀的時(shí)候，處理器停留在狀態(tài)檢查周期 InterruptDriven I/O ? Processor issues an I/O mand to a module 處理器給模塊發(fā)送一個(gè) I/O命令 – and then goes on to do some other useful ? The I/O module will then interrupt the processor to request service when it is ready to exchange data with the I/O模塊準(zhǔn)備好與處理器將換數(shù)據(jù)時(shí)，他將打斷處理器并請求服務(wù) Interrupt Driven I/O ? Eliminates needless waiting消除不必要的等待 – But everything passes through 西都得經(jīng)過處理器處理 Direct Memory Access ? Performed by a separate module on the system（可能）由系統(tǒng)（總線）中的獨(dú)立模塊完成 ? When needing to read/write processor issues a mand to DMA module with:當(dāng)處理器需要讀寫時(shí)，他給 DMA模塊產(chǎn)生一條命令，發(fā)送以下信息： – Whether a read or write is requested是否請求讀寫 – The address of the I/O device involved相關(guān) I/O設(shè)備的地址 – The starting location in memory to read/write開始讀寫的存儲單元 – The number of words to be read/written需要讀寫的字?jǐn)?shù) Direct Memory Access ? I/O operation delegated to DMA module（處理器把） I/O操作委托給 DMA模塊 ? Processor only involved when beginning and ending 輸開始 /結(jié)束時(shí)，處理器才會參與 ? Much more 兩者更有效
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