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比如說一般 32位的 DSP能在一個指令周期內(nèi)運算完一個 32位數(shù)乘 32位數(shù)積再加一個 32 位數(shù),應(yīng)用于某些對實時處理要求較高的場合。常用于手機、路由器等等。 VCC:電源 +5V輸入 VSS: GND接地。 8751燒寫內(nèi)部 EPROM時,利用此腳輸入 21V的燒寫電壓。 內(nèi)部 ROM讀取時, PSEN不動作; 外部 ROM讀取時,在每個機器周期會動作兩次; 外部 RAM讀取時,兩個 PSEN脈沖被跳過不會輸出; 外接 ROM時,與 ROM的 OE腳相接。 在沒有訪問外部存儲器期間, ALE以 1/6振蕩周期頻率輸出(即 6分頻),當訪問外部存儲器以 1/12振蕩周期輸出( 12分頻)。(在后面關(guān)于擴展的課程中我們就會看到 8051擴展 EEPROM電路,在圖中 ALE與 74LS373鎖存器的 G相連接,當 CPU對外部進行存取時,用以鎖住地址的低位地址,即 P0口輸出。 P2口有兩個功能: 擴展外部存儲器時,當作地址總線使用 做一般 I/O口使用,其內(nèi)部有上拉電阻; P3口有兩個功能: 除了作為 I/O使用外(其內(nèi)部有上拉電阻),還有一些特殊功能,由特殊寄存器來設(shè)置,具體功能請參考我們后面的引腳說明。 ~ P3口 8位雙向口線(在引腳的 10~17號端子)。 80年代以來,單片機發(fā)展迅速,各類新產(chǎn)品不斷涌現(xiàn),出現(xiàn)了許多高性能新型機種,現(xiàn)已逐漸成為工廠自動化和各控制領(lǐng)域的支柱產(chǎn)業(yè)之一。s largest MCU shipments, followed by Freescale microcontroller. ARM is actually 32bit microcontroller, its internal resources (registers and peripheral functions) than in 8051 and PIC, AVR should be a lot more, with the puter39。 2, external ROM reading at each machine cycle will move twice。 P3 port has two functions: As well as I / O using the external (the internal pullup resistor), there are some special features, from a special register to set the specific features please refer to our explanation behind the pin. Internal EPROM of the microcontroller chip (for example, 8751), for the writing process required to provide specialized programming and programming pulse power, these signals are also provided in the form from the signal pin, and Namely: programming pulse: 30 feet (ALE / PROG) Programming voltage (25V): 31 feet (EA / Vpp) In introducing the four I / O port referred to a pullup resistor Then, pullup resistor is what Dongdong do? What role does he play? Said the resistance that is of course, is a resistor, when as an input, the pullup resistor pulled its potential, if the input is low you can provide a current source。 Therefore, if the P0 port as long as the input, in the high impedance state, only an external pullup resistor to be effective. ALE / PROG address latch control signal: in a system is extended, A