曼徹斯特編碼的接收C51程序

曼碼接收程序，常用在無線信號的編碼與解碼中，給大家分享：rxi(){// this routine gets called every time TMR0 overflowsif(T0IF)  //定時器中斷程序{TMR0 = PERIOD;             // 裝計時器初值T0IF = 0;     // 清定時器溢出標志XTMR++;                     // 外部的系統時鐘計時器加1RFcount++;     // 脈沖寬度計數器加1return;}if(RAIF)  //端口電平變化中斷程序{if (RFFull)                 // 如果接收位滿就退出return;RFBit = RFIn;               // 取樣信號接收的值RAIF = 0;switch (RFstate)            // 當前狀態{case TRFDATAUP:switch (RFcount){ case 4:case 5:  case 6:case 7:PORTA = PORTA;//啟動端口電平中斷break;case 8:case 9:case 10:case 11:case 12:B[Bptr] = 1;              // rotate if ( RFBit==0)  //如是有效的下跳變則該位的數據值為1,上跳變為0{ B[Bptr]+=1;          // shift in bit}if ( ( ++BitCount  7) == 0)Bptr++;                 // advance one byte if (BitCount == NBIT){RFstate = TRFreset;     // finished receiving RFFull = 1;} RFcount=0; //重新記時PORTA = PORTA;//啟動端口電平中斷break;default:  //超時或不足則退出接收RFstate = TRFSYNC;        // reset state machine in all other casesRFcount = 0;Bptr = 0;BitCount = 0;PORTA = PORTA;//啟動端口電平中斷}break;case TRFSYNC:if ( RFBit){ // rising edge detected  +---+                +---..//                       |   |  -Theader->   |   //                           +----------------+if ( ( RFcount  SHORT_HEAD) || ( RFcount >= LONG_HEAD)){RFstate = TRFreset;PORTA = PORTA;//啟動端口電平中斷break;                  // too short/long, no header}else{RFcount =0;             // restart counterRFstate= TRFDATAUP;PORTA = PORTA;//啟動端口電平中斷}}else{ // still lowRFcount=0;PORTA = PORTA;//啟動端口電平中斷}break;case TRFreset:default:RFstate = TRFSYNC;        // reset state machine in all other casesRFcount = 0;Bptr = 0;BitCount = 0;PORTA = PORTA;//啟動端口電平中斷break;} // switch} //電平中斷   } // rxi void InitReceiver(){IOCA = 2;T0IF = 0;T0IE = 1;                   // TMR0 overflow interruptRAIE = 1;     //使能端口電平變化中斷GIE = 1;                    // enable interruptsRFstate = TRFreset;         // reset state machine in all other casesRFFull = 0;                 // start with buffer emptyXTMR = 0;                   // start extended timerTMR0 = PERIOD;             // 裝計時器初值PORTA = PORTA;//啟動端口電平中斷}