CALCUL DE LRC POUR TRAMES MODBUS ASCII

private static string LRC(String trame_test)
{
    Char[] instructions = new Char[trame_test.Length / 2];
    for (Int32 i = 0; i < trame_test.Length; i += 2)
        instructions[i / 2] = (Char)Byte.Parse(trame_test.Substring(i, 2),
            System.Globalization.NumberStyles.HexNumber );
    int LRC = 0;
    for (int i = 0; i < instructions.Length; i++)
        LRC += (int)instructions[i];
    LRC = 255 - LRC + 1;
    return LRC.ToString("x2");
}

//This function can be call by this instruction on a cubloc communication context :
//trame = ":" + instruction + LRC(instruction);