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function crc_16($Str)
{
$crc_ = '0xFFFF';
$a001_ = '0xA001'; 

$Pos_ = 0;

for ($Sf = 1; $Sf <= (strlen ($Str) / 2); $Sf ++)
  {  $BoM = hexdec($Str[$Pos_] . $Str[$Pos_ + 1]);
     $Pos_ ++; $Pos_ ++;
     $crc_ = $crc_ ^ $BoM;
     for ($Sb = 1; $Sb <= 8; $Sb ++)
      {  $droppedbit = $crc_ & 1;
         $crc_x = 0;
         if ($crc_ & 1)  $crc_x = 32768;
         $crc_ = $crc_ >> 1;
         $crc_ = $crc_ | $crc_x;
         if ($droppedbit = 1)  $crc_ = crc_ ^ $a001;
       }
  }
return $crc_;
}

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function crc = crc16(str)

crc = uint16(hex2dec('FFFF'));
a001 = uint16(hex2dec('A001'));

for i=1:length(str)
    ByteOfMessage = str(i);
    crc = bitxor(crc,ByteOfMessage);
    for j=1:8
       droppedbit=bitget(crc,1);
       crc = bitshift(crc,-1);
       if droppedbit
           crc = bitxor(crc,a001);
       end        
    end
end  

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if ($droppedbit = 1)  $crc_ = crc_ ^ $a001;