******************************************************************/

#define    Wait1us        _nop_();
#define    Wait2us        {_nop_();_nop_();}
#define    Wait4us        {Wait2us;Wait2us;}
#define    Wait8us        {Wait4us;Wait4us;}
#define    Wait10us  {Wait8us;Wait2us;}

＃i nclude "INTRINS.H"

/************定义接口总线**************/
sbit Clock = P3 ^ 4; //时钟口线
sbit DataIn = P3 ^ 2; //数据输入口线
sbit DataOut = P3 ^ 5; //数据输出口线
sbit ChipSelect = P3 ^ 3; //片选口线
sbit EOC = P2 ^ 7; //转换完成口线
/************接口总线定义结束**********/

/*********函数名称：ADCSelChannel********
*
*功能：转换指定通道的模拟量为数字量
*
*说明：
*
*位置：1
*
****************************************/
unsigned int ADCSelChannel(unsigned char Channel)
{
 unsigned int ConvertValue;
 unsigned char i, Chan;
 unsigned char ConvertValueL, ConvertValueH;
 unsigned char delay;
 
 ConvertValueL = ConvertValueH = 0; //初始化转换结果
 delay = 0;
 if (EOC)
 {
  Clock = 0;
  ChipSelect = 1;
  Wait2us;
  ChipSelect = 0;
  Wait2us;
  Channel = Channel << 4;
  for (i = 0; i < 4; i ++) //输入需要转换的通道的编码
  {
   Chan = Channel;
   Chan = Chan >> 7;
   DataIn = (bit)Chan;
   Wait2us;
   Clock = 1;
   Clock = 0;
   Channel = Channel << 1;
  }
  for (i = 0; i < 6;i ++) //输入转换时钟
  {
   Clock = 1;
   Clock = 0;
  }
  ChipSelect = 1;
  //开始检测转换结束标志，或者转换超时出错
  while ((!EOC) && (delay < 10))
  {
   Wait10us;
   delay ++;
  }
  if (delay == 10)
  {
   return (0xFFFF); //转换超时，返回错误代码
  }
  else
  {
   Wait10us;
   Clock = 0;
   ChipSelect = 1;
   Wait1us;
   ChipSelect = 0;
   Wait1us;
   for (i = 0; i < 2; i ++) //读取高二位bit值
   {
    Clock = 1;
    DataOut = 1;
    ConvertValueH <<= 1;
    if (DataOut)
      ConvertValueH |= 0x1;
    Clock = 0;
    Wait1us;
   } 
   for (i = 0; i < 8; i ++) //读取低八位bit值
   {
    Clock = 1;
    DataOut = 1;
    ConvertValueL <<= 1;
    if (DataOut)
      ConvertValueL |= 0x1;
    Clock = 0;
    Wait1us;
   } 
   ChipSelect=1;
   ConvertValue = ConvertValueH;
   ConvertValue <<= 8;
   ConvertValue |= ConvertValueL;
   return (ConvertValue); //返回转换结果
  }
 }
}
/************ADCSelChannel函数结束**********/