【正文】 輸入（A0, A1和A3），并當(dāng)使能時，提供8個互斥的低有效輸出（Y0至Y7）。任選一個低有效使能輸入端作為數(shù)據(jù)輸入，而把其余的使能輸入端作為選通端，則74HC138亦可充當(dāng)一個8輸出多路分配器，未使用的使能輸入端必須保持綁定在各自合適的高有效或低有效狀態(tài)。 通過控制選通腳來級聯(lián)，使之?dāng)U展到十六位。 LED顯示屏按顯示器件分類可分以下幾種： LED數(shù)碼顯示屏：顯示器件為7段碼數(shù)碼管，適于制作時鐘屏、利率屏等，顯示數(shù)字的電子顯示屏。LED 點陣圖文顯示屏單塊模塊控制驅(qū)動12塊（最多可控制24塊）8*8點陣，它可采用“級連”的方式組成任意點陣大顯示屏。一根橫柱：對應(yīng)的行置0，而列則采用掃描的方法來實現(xiàn)。把每個 LED 的陰極和陽極都引出來，就可以對點陣中的任何一個LED加以控制，達到要顯示的效果。16*16點陣的陽極驅(qū)動由P0口經(jīng)輸出緩沖器74LS273構(gòu)成，在本設(shè)計中需要用兩片，分別送出上8行和下8行的字型碼。第四章 LED字幕顯示系統(tǒng)軟件設(shè)計本設(shè)計的系統(tǒng)軟件包括單片機控制程序、中斷子程序、顯示子程序等幾個模塊。是否顯示完？開始初始化調(diào)用顯示程序調(diào)整數(shù)據(jù)指針圖41 程序開發(fā)流程圖AT89C51單片機是8位機，每次只能送出8位數(shù)據(jù)，因此要向16*16點陣送出16行陽極驅(qū)動，需要送兩次，或先送上8行，或先送下8行，為了能夠?qū)崿F(xiàn)每一列字型碼的完整顯示，采用74LS273進行鎖存，否則會出現(xiàn)字型殘缺現(xiàn)象。主程序中主要是逐字顯示程序，具體說明如下所示：void main(void) //主函數(shù){ int8 i。 TMOD=0x01。i++) //顯示左半邊屏幕 { clk=0。 //=0,=1 選中U2, 輸出掃描碼給U6 P0=*(p+offset+2*i)。 clk=1。i16。 P2=(i8)|0x20。 clk=1。接下來，程序就會進入一個無限循環(huán)的狀態(tài)以等待中斷的發(fā)生。顯示完成后，程序就會跳到主程序的斷點處，繼續(xù)執(zhí)行主程序下面的程序。 //開始計數(shù)………void delay(void){ int16 i。 }void timer0() interrupt 1 using 3{ TF0=0。 } else { offset+=2。 圖51 在keil軟件中編程和調(diào)試 用PROTEUS 繪制原理圖運行 Proteus 的 ISIS 程序后，進入該仿真軟件的主界面。圖52 運行 Proteus ISIS的主界面 圖53 16*16 LED 完整電路圖 PROTEUS 對單片機內(nèi)核的仿真在source 菜單的Define code generation tools 菜單命令下，選擇程序編譯的工具、路徑、擴展名等項目。Proteus 與其它單片機仿真軟件不同的是，它不僅能仿真單片機外圍電路或沒有單片機參與的其它電路的工作情況，也能仿真單片機CPU的工作情況。本設(shè)計的仿真結(jié)果如圖55所示。雖然本設(shè)計使用了四塊8*8LED點陣，電路簡單，但是已經(jīng)包涵了LED顯示屏的電路基本原理和基本程序，只要擴展單片機的I/O接口，并增加一些LED點陣和相關(guān)芯片，就能設(shè)計出更大面積、更多花樣的LED顯示屏。在這次設(shè)計中，我從中學(xué)到了不少的知識，以前對單片機了解甚少，在這次設(shè)計中，對單片機有了一個較全面的認識、學(xué)習(xí)、掌握，也能對一些簡單程序進行編寫。102U6U9LED點陣8*8點陣4UU11譯碼器74LS2732U12反相器74041RP1排阻*81X1晶振CRYSTAL1K復(fù)位按鈕BUTTON1X1晶振CRYSTAL1舊底圖總號更改標(biāo)記數(shù)量更改單號簽名日期底圖總號擬 制LED字幕顯示系統(tǒng)設(shè)計審 校日期簽名等級標(biāo)記第1張共1張標(biāo)準化批 準附錄3 程序清單include //define int8 unsigned char //宏定義define int16 unsigned intdefine int32 unsigned longsbit clk=P2^7。 //變量聲明/***********************************************************//*******************字幕編碼*******************************//**********************************************************/int8 code table[][32]={{0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00},/* */{0x11,0x80,0x16,0x00,0xFF,0xFE,0x14,0x00,0x12,0x02,0x00,0x42,0x08,0x44,0x04,0x98,0xFF,0xE0,0x00,0x00,0xFF,0xFC,0x01,0x02,0x04,0xC2,0x18,0x62,0x10,0x0E,0x00,0x00},/*桃,0*/{0x01,0x00,0x21,0x20,0x22,0x20,0x23,0x20,0x25,0x20,0x29,0x22,0x31,0x21,0xFF,0x7E,0x31,0xA0,0x29,0x20,0x25,0x20,0x24,0x20,0x22,0x20,0x23,0x20,0x02,0x20,0x00,0x00},/*李,1*/{0x08,0x10,0x86,0x1F,0x60,0xE0,0x07,0x00,0x20,0x00,0x25,0xFF,0x25,0x10,0xF7,0xE0,0x25,0x28,0x25,0x10,0x27,0xE0,0xF5,0x22,0x25,0x11,0x25,0xFE,0x24,0x00,0x00,0x00},/*滿,2*/{0x00,0x00,0x02,0x01,0x42,0x02,0x42,0x04,0x42,0x08,0x42,0x10,0x42,0x60,0x7F,0x80,0x42,0x40,0x42,0x20,0x42,0x10,0x42,0x08,0x42,0x0C,0x42,0x06,0x02,0x04,0x00,0x00},/*天,3*/{0x00,0x00,0x40,0x00,0x40,0x00,0x40,0x00,0x40,0x00,0x40,0x00,0x40,0x00,0x7F,0xFE,0x44,0x00,0x46,0x00,0x43,0x80,0x41,0x00,0x40,0x00,0xC0,0x00,0x40,0x00,0x00,0x00},/*下,4*/{0x00,0x00,0x00,0x00,0x00,0x1A,0x00,0x1C,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00},/*，,5*/{0x00,0x00,0x00,0x0C,0x00,0x30,0xFF,0x00,0x81,0x3C,0x91,0x02,0x93,0x02,0x95,0x42,0xF9,0x32,0x95,0x02,0x93,0x02,0x91,0x0E,0xFF,0x20,0x00,0x1C,0x00,0x08,0x00,0x00},/*恩,6*/{0x0E,0x00,0x00,0x00,0xFF,0xFF,0x10,0x00,0x0A,0x00,0x22,0x00,0x2A,0xFF,0x2A,0xA8,0x2A,0xA8,0xFE,0xA8,0x2A,0xAA,0x2A,0xA9,0x2A,0xFE,0x22,0x00,0x02,0x00,0x00,0x00},/*情,7*/{0x01,0x00,0x02,0x00,0x1F,0xFE,0xE8,0x00,0x40,0x00,0x1F,0xF8,0x00,0x12,0x80,0x22,0x70,0x44,0x20,0x84,0x00,0x08,0x00,0x30,0xFF,0xC0,0x00,0x30,0x00,0x0E,0x00,0x00},/*似,8*/{0x08,0x20,0x06,0x20,0x80,0xFF,0x6F,0x00,0x00,0x80,0x08,0x80,0x1F,0xF8,0xE8,0x88,0x2C,0xC8,0x2A,0xA8,0x28,0x8A,0x28,0x89,0x2F,0xFE,0x20,0x88,0x20,0x88,0x00,0x00},/*海,9*/{0x08,0x20,0x86,0x3F,0x60,0xC0,0x07,0x04,0x00,0x04,0x64,0x88,0x44,0x88,0x58,0x90,0x40,0xA0,0x43,0xFF,0x50,0xA0,0x48,0x90,0x4C,0x98,0x60,0x8C,0x40,0x08,0x00,0x00},/*深,10*/{0x00,0x00,0x00,0x00,0x00,0x00,0x0F,0xFA,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00},/*！,11*/{0x10,0x40,0x10,0x80,0x91,0x00,0x73,0xFF,0x15,0x00,0x18,0xC1,0x00,0x02,0x7F,0x0C,0x41,0xF0,0x41,0x00,0x41,0x00,0x41,0xFE,0x7F,0x01,0x00,0x01,0x00,0x0F,0x00,0x00},/*祝,12*/{0x00,0x40,0x04,0x40,0x04,0x40,0x08,0x80,0x10,0xFE,0xF1,0x42,0x2D,0x42,0x22,0x42,0x22,0x42,0x25,0x42,0x39,0x42,0x20,0xFE,0x00,0x80,0x00,0xC0,0x00,0x80,0x00,0x00},/*各,13*/{0x00,0x80,0x03,0x00,0x0C,0x00,0x37,0xFE,0xC0,0x04,0x54,0x04,0x13,0x04,0x90,0xE4,0x50,0x04,0x70,0x0C,0x10,0x74,0x17,0x84,0x12,0x04,0x10,0x04,0x00,0x04,0x00,0x00},/*位,14*/{0x02,0x10,0x22,0x10,0x22,0x20,0x22,0x20,0x22,0x40,0x22,0x7C,0xFE,0x92,0x23,0x12,0x23,0x22,0x22,0x22,0x26,0x42,0x2A,0x42,0x72,0x02,0x22,0x0E,0x02,0x00,0x00,0x00},/*老,15*/{0x00,0x02,0x3F,0xE4,0x00,0x08