//-----------------crc8()-------------------------

uint8 crc8(uint8*buf, uint8 data_byte)
   {
   uint8 crc=0x00;
   uint8 data_bit=0x80;
   
   while(data_byte>0)
      {
      if(((crc&0x01)!=0)!=((buf[data_byte]&data_bit)!=0))
         {
         crc>>=1;
         crc^=0xCD;