【文章內容簡介】 L初值為 65535，高八位為 65535除以 256，余數(shù)放在低八位；計數(shù)器選擇 16位的定時模式；允許 T1 中斷，開定時器。 鍵掃描子程序 鍵掃描子程序的任務是檢查 3個按鍵是否有鍵按下，若有鍵按下，則執(zhí)行相應的功能。在這里， 3 個按鍵分別用于頻率增加、頻率減少和正弦波和三角波的選擇功能。鍵掃描子程序流程圖和程序如下。 圖 鍵掃描子程序流程圖 /******************************************* 鍵 掃 描 子 函 數(shù)**********************************/ keyscan() 簡易低頻信號源設計 7 { keyword=keyamp。0x07。 if(keyword!=0x07) { while((keyamp。0x07)!=0x07)。 switch(keyword) { case6:{if(THHL=65235)THHL=65535。else{THHL=THHL+255。}break。} case5:{if(THHL=500)THHL=0。else{THHL=THHL255。}break。} case3:{sin_thr=~sin_thr。break。} default:{break。} } } } // 波形數(shù)據(jù)產生子程序 波形數(shù)據(jù)產生子程序是定時器 T1的中斷程序。當定時器計數(shù)溢出時，發(fā)生一次中斷。當發(fā)生中斷時，單片機將按次序將波形數(shù)據(jù)表中的波形數(shù)據(jù)一一送入到 DAC0832，DAC0832再根據(jù)輸入的數(shù)據(jù)大小輸出對 應的的電壓。波形數(shù)據(jù)產生子程序流程圖和程序如下。 //********************************************T1 中斷函數(shù)*********************************/ void time_intt1(void) interrupt 3 { EA=0。TR1=0。TH1=THHL/256。TL1=THHL%256。TR1=1。 if(sin_thr){dataout=sin_tab[n]。} else{dataout=thr_tab[n]。} if(n=255){n=0。}else{n++。} ww=~ww。 EA=1。 } //***************************************** 結束*****************************************、 沈陽工程學院課程設計（論文） 8 圖 波形數(shù)據(jù)產生子程序流程 波形查找表程序 三角波查找表 /***************************三角波數(shù)據(jù)表 ****************************/ uchar code thr_tab[256]= { 0x80,0x81,0x82,0x83,0x84,0x85,0x86,0x87, 0x88,0x89,0x8A,0x8B,0x8C,0x8D,0x8E,0x8F, 0x90,0x91,0x92,0x93,0x94,0x95,0x96,0x97, 0x98,0x99,0x9A,0x9B,0x9C,0x9D,0x9E,0x9F, 0xA0,0xA1,0xA2,0xA3,0xA4,0xA5,0xA6,0xA7, 0xA8,0xA9,0xAA,0xAB,0xAC,0xAD,0xAE,0xAF, 0xB0,0xB1,0xB2,0xB3,0xB4,0xB5,0xB6,0xB7, 0xB8,0xB9,0xBA,0xBB,0xBC,0xBD,0xBE,0xBF, 0xBF,0xBE,0xBD,0xBC,0xBB,0xBA,0xB9,0xB8, 0xB7,0xB6,0xB5,0xB4,0xB3,0xB2,0xB1,0xB0, 0xAF,0xAE,0xAD,0xAC,0xAB,0xAA,0xA9,0xA8, 0xA7,0xA6,0xA5,0xA4,0xA3,0xA2,0xA1,0xA0, 0x9F,0x9E,0x9D,0x9C,0x9B,0x9A,0x99,0x98, 0x97,0x96,0x95,0x94,0x93,0x92,0x91,0x90, 0x8F,0x8E,0x8D,0x8C,0x8B,0x8A,0x89,0x88, 簡易低頻信號源設計 9 0x87,0x86,0x85,0x84,0x83,0x82,0x81,0x80, 0x7F,0x7E,0x7D,0x7C,0x7B,0x7A,0x79,0x78, 0x77,0x76,0x75,0x74,0x73,0x72,0x71,0x70, 0x6F,0x6E,0x6D,0x6C,0x6B,0x6A,0x69,0x68, 0x66,0x66,0x65,0x64,0x63,0x62,0x61,0x60, 0x5F,0x5E,0x5D,0x5C,0x5B,0x5A,0x59,0x58, 0x55,0x55,0x55,0x54,0x53,0x52,0x51,0x50, 0x4F,0x4E,0x4D,0x4C,0x4B,0x4A,0x49,0x48, 0x44,0x44,0x45,0x44,0x43,0x42,0x41,0x40, 0x40,0x41,0x42,0x43,0x44,0x45,0x46,0x47, 0x48,0x49,0x4A,0x4B,0x4C,0x4D,0x4E,0x4F, 0x50,0x51,0x52,0x53,0x54,0x55,0x56,0x57, 0x58,0x59,0x5A,0x5B,0x5C,0x5D,0x5E,0x5F, 0x60,0x61,0x62,0x63,0x66,0x65,0x66,0x67, 0x68,0x69,0x6A,0x6B,0x6C,0x6D,0x6E,0x6F, 0x70,0x71,0x72,0x73,0x77,0x75,0x76,0x77, 0x78,0x79,0x7A,0x7B,0x7C,0x7D,0x7E,0x7F}。 // 正弦波查找表 /*****************************正弦波數(shù)據(jù)表 ****************************/ uchar code sin_tab[256]= {0x80,0x83,0x85,0x88,0x8A,0x8D,0x8F,0x92, 0x94,0x97,0x99,0x9B,0x9E,0xA0,0xA3,0xA5, 0xA7,0xAA,0xAC,0xAE,0xB1,0xB3,0xB5,0XB7, 0xB9,0XBB,0xBD,0XBF,0xC1,0xC3,0xC5,0xC7, 0xC9,0xCB,0xCC,0xCE,0xD0,0xD1,0xD3,0xD4, 0xD6,0xD7,0xD8,0xDA,0xDB,0xDC,0xDD,0xDE, 0xDF,0xE0,0xE1,0xE2,0xE3,0xE3,0xE4,0xE4, 0xE5,0xE5,0xE6,0xE6,0xE7,0xE7,0xE7,0xE7, 0xE7,0xE7,0xE7,0xE7,0xE6,0xE6,0xE5,0xE5, 0xE4,0xE4,0xE3,0xE3,0xE2,0xE1,0xE0,0xDF, 0xDE,0xDD,0xDC,0xDB,0xDA,0xD8,0xD7,0xD6, 0xD4,0xD3,0xD1,0xD0,0xCE,0xCC,0xCB,0xC9, 0xC7,0xC5,0xC3,0xC1,0xBF,0xBD,0xBB,0xB9, 0xB7,0xB5,0xB3,0xB1,0xAE,0xAC,0xAA,0xA7, 0xA5,0xA3,0xA0,0x9E,0x9B,0x99,0x97,0x94, 0x92,0x8F,0x8D,0x8A,0x88,0x85,0x83,0x80, 0x7D,0x7B,0x78,0x76,0x73,0x71,0x6E,0x6C, 0x69,0x67,0x65,0x62,0x60,0x5D,0x5B,0x59, 0x56,0x54,0x52,0x4F,0x4D,0x4B,0x49,0x47, 0x45,0x43,0x41,0x3F,0x3D,0x3B,0x39,0x37, 沈陽工程學院課程設計（論文） 10 0x35,0x34,0x32,0x30,0x2F,0x2D,0x2C,0x2A, 0x29,0x28,0x26,0x25,0x24,0x23,0x22,0x21, 0x20,0x1F,0x1E,0x1D,0x1D,0x1C,0x1C,0x1B, 0