Delphi Modbus RTU CRC16校验码

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function CheckCrc16(const ABuf; ALen: Integer): Boolean;
var
  uwTemp: WORD;
  i, j: BYTE;
  P: PByte;
begin
  Result := False;

  P := PByte(@ABuf);

  uwTemp := $FFFF;
  for i := 1 to ALen do
  begin
    uwTemp := uwTemp xor P^;
    for j := 1 to 8 do
    begin
      if (uwTemp and 1) = 1 then
        uwTemp := (uwTemp shr 1) xor $A001
      else
        uwTemp := uwTemp shr 1
    end;
    Inc(P);
  end;

  if P^ = BYTE(uwTemp) then
  begin
    Inc(P);
    if P^ = BYTE(uwTemp shr 8) then
    begin
      Result := True;
    end
  end
end;