unit1.pas

用DELPHI写的Modbus RTU CRC检验方法

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, Buttons, StdCtrls;

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    SpeedButton1: TSpeedButton;
    Label3: TLabel;
    Label4: TLabel;
    procedure SpeedButton1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
function ModBusCRC(Data: string): string; //生成modbus CRC数据

var
  Form1: TForm1;

implementation

{$R *.dfm}


function ModBusCRC(Data: string): string; //生成modbus CRC数据
var
  CRC16Lo, CRC16Hi, CL, CH, UseHi, UseLo: Dword;
  i, index: integer;
begin
  CRC16Lo := $FF; //CRC16Lo为CRC寄存器低8位
  CRC16Hi := $FF; //CRC16Hi为CRC寄存器高8位
  CL := $1;
  CH := $A0; //  A001 H 是CRC－16多项式代码
  for i := 1 to Length(Data) do
  begin
    CRC16Lo := CRC16Lo xor ord(Data[i]); //每一个数据与CRC寄存器异或
    for index := 0 to 7 do
    begin
      UseHi := CRC16Hi;
      UseLo := CRC16Lo;
      CRC16Hi := CRC16Hi shr 1;
      CRC16Lo := CRC16Lo shr 1; //右移一位
      if ((UseHi and $1) = $1) then //如果高位字节最后一位是1的话
        CRC16Lo := CRC16Lo or $80; //低位字节右移后前面补1

      if ((UseLo and $1) = $1) then //如果LSB 为1，则与多项式进行异或
      begin
        CRC16Hi := CRC16Hi xor CH;
        CRC16Lo := CRC16Lo xor CL;
      end;
    end;
  end;

  Result := IntToHex(CRC16Lo, 2) + IntToHex(CRC16Hi, 2);
end;

procedure TForm1.SpeedButton1Click(Sender: TObject);
begin
 Label2.Caption :=ModBusCRC(Edit1.Text); 
end;

end.