對于這段代碼幾個地方不清楚，希望哪個老哥幫忙解釋解釋
1 、((BYTE *)&count1)[3] = CCAP0L; //保存本次的捕獲值
((BYTE *)&count1)[2] = CCAP0H;
((BYTE *)&count1)[1] = cnt;
((BYTE *)&count1)[0] = 0;
這是將count1這個LONG INT 數強制轉換成一個數組？最后count1等于多少呢
2、 if (CF && ((CCAP0H & 0x80) == 0))
{
CF = 0;
cnt++;
}
這一段的作用是什么？
3、老哥們能不能詳細說說捕獲功能的具體運作流程，小子拜謝了
- //本示例在Keil開發環境下請選擇Intel的8058芯片型號進行編譯
- //若無特別說明,工作頻率一般為11.0592MHz
- #include "reg51.h"
- #include "intrins.h"
- #define FOSC 11059200L
- typedef unsigned char BYTE;
- typedef unsigned int WORD;
- typedef unsigned long DWORD;
- sfr P0M1 = 0x93;
- sfr P0M0 = 0x94;
- sfr P1M1 = 0x91;
- sfr P1M0 = 0x92;
- sfr P2M1 = 0x95;
- sfr P2M0 = 0x96;
- sfr P3M1 = 0xb1;
- sfr P3M0 = 0xb2;
- sfr P4M1 = 0xb3;
- sfr P4M0 = 0xb4;
- sfr P5M1 = 0xC9;
- sfr P5M0 = 0xCA;
- sfr P6M1 = 0xCB;
- sfr P6M0 = 0xCC;
- sfr P7M1 = 0xE1;
- sfr P7M0 = 0xE2;
- sfr P_SW1 = 0xA2; //外設功能切換寄存器1
- #define CCP_S0 0x10 //P_SW1.4
- #define CCP_S1 0x20 //P_SW1.5
- sfr CCON = 0xD8; //PCA控制寄存器
- sbit CCF0 = CCON^0; //PCA模塊0中斷標志
- sbit CCF1 = CCON^1; //PCA模塊1中斷標志
- sbit CR = CCON^6; //PCA定時器運行控制位
- sbit CF = CCON^7; //PCA定時器溢出標志
- sfr CMOD = 0xD9; //PCA模式寄存器
- sfr CL = 0xE9; //PCA定時器低字節
- sfr CH = 0xF9; //PCA定時器高字節
- sfr CCAPM0 = 0xDA; //PCA模塊0模式寄存器
- sfr CCAP0L = 0xEA; //PCA模塊0捕獲寄存器 LOW
- sfr CCAP0H = 0xFA; //PCA模塊0捕獲寄存器 HIGH
- sfr CCAPM1 = 0xDB; //PCA模塊1模式寄存器
- sfr CCAP1L = 0xEB; //PCA模塊1捕獲寄存器 LOW
- sfr CCAP1H = 0xFB; //PCA模塊1捕獲寄存器 HIGH
- sfr CCAPM2 = 0xDC; //PCA模塊2模式寄存器
- sfr CCAP2L = 0xEC; //PCA模塊2捕獲寄存器 LOW
- sfr CCAP2H = 0xFC; //PCA模塊2捕獲寄存器 HIGH
- sfr PCA_PWM0 = 0xf2; //PCA模塊0的PWM寄存器
- sfr PCA_PWM1 = 0xf3; //PCA模塊1的PWM寄存器
- sfr PCA_PWM2 = 0xf4; //PCA模塊2的PWM寄存器
- BYTE cnt; //存儲PCA計時溢出次數
- DWORD count0; //記錄上一次的捕獲值
- DWORD count1; //記錄本次的捕獲值
- DWORD length; //存儲信號的時間長度(count1 - count0)
- void main()
- {
- P0M0 = 0x00;
- P0M1 = 0x00;
- P1M0 = 0x00;
- P1M1 = 0x00;
- P2M0 = 0x00;
- P2M1 = 0x00;
- P3M0 = 0x00;
- P3M1 = 0x00;
- P4M0 = 0x00;
- P4M1 = 0x00;
- P5M0 = 0x00;
- P5M1 = 0x00;
- P6M0 = 0x00;
- P6M1 = 0x00;
- P7M0 = 0x00;
- P7M1 = 0x00;
- ACC = P_SW1;
- ACC &= ~(CCP_S0 | CCP_S1); //CCP_S0=0 CCP_S1=0
- P_SW1 = ACC; //(P1.2/ECI, P1.1/CCP0, P1.0/CCP1, P3.7/CCP2)
- // ACC = P_SW1;
- // ACC &= ~(CCP_S0 | CCP_S1); //CCP_S0=1 CCP_S1=0
- // ACC |= CCP_S0; //(P3.4/ECI_2, P3.5/CCP0_2, P3.6/CCP1_2, P3.7/CCP2_2)
- // P_SW1 = ACC;
- //
- // ACC = P_SW1;
- // ACC &= ~(CCP_S0 | CCP_S1); //CCP_S0=0 CCP_S1=1
- // ACC |= CCP_S1; //(P2.4/ECI_3, P2.5/CCP0_3, P2.6/CCP1_3, P2.7/CCP2_3)
- // P_SW1 = ACC;
- CCON = 0; //初始化PCA控制寄存器
- //PCA定時器停止
- //清除CF標志
- //清除模塊中斷標志
- CL = 0; //復位PCA寄存器
- CH = 0;
- CCAP0L = 0;
- CCAP0H = 0;
- CMOD = 0x09; //設置PCA時鐘源為系統時鐘,且使能PCA計時溢出中斷
- CCAPM0 = 0x21; //PCA模塊0為16位捕獲模式(上升沿捕獲,可測從高電平開始的整個周期),且產生捕獲中斷
- // CCAPM0 = 0x11; //PCA模塊0為16位捕獲模式(下降沿捕獲,可測從低電平開始的整個周期),且產生捕獲中斷
- // CCAPM0 = 0x31; //PCA模塊0為16位捕獲模式(上升沿/下降沿捕獲,可測高電平或者低電平寬度),且產生捕獲中斷
- CR = 1; //PCA定時器開始工作
- EA = 1;
- cnt = 0;
- count0 = 0;
- count1 = 0;
- while (1);
- }
- void PCA_isr() interrupt 7 using 1
- {
- if (CCF0)
- {
- CCF0 = 0;
- if (CF && ((CCAP0H & 0x80) == 0))
- {
- CF = 0;
- cnt++;
- }
- count0 = count1; //備份上一次的捕獲值
- ((BYTE *)&count1)[3] = CCAP0L; //保存本次的捕獲值
- ((BYTE *)&count1)[2] = CCAP0H;
- ((BYTE *)&count1)[1] = cnt;
- ((BYTE *)&count1)[0] = 0;
- length = count1 - count0; //計算兩次捕獲的差值,即得到時間長度
- ((BYTE *)&length)[0] = 0;
- }
- if (CF)
- {
- CF = 0;
- cnt++; //PCA計時溢出次數+1
- }
- }
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