C# Modbus RTU CRC 구하기

C# Modbus RTU 통신할 때 CRC 를 구하는 함수 입니다~

ModbusTCP/IP 와는 다르게 RTU는 CRC를 구해서 같이 요청을 해야 한다는..

그리고 Modbus TCP/IP 프로토콜 형식과 RTU 프로토콜 형식은 조금 다르다는 것!

  class TModbusRTU
    {
        private readonly ushort[] wCRCTable =
        {
        0X0000, 0XC0C1, 0XC181, 0X0140, 0XC301, 0X03C0, 0X0280, 0XC241, 0XC601, 0X06C0,
        0X0780, 0XC741, 0X0500, 0XC5C1, 0XC481, 0X0440, 0XCC01, 0X0CC0, 0X0D80, 0XCD41,
        0X0F00, 0XCFC1, 0XCE81, 0X0E40, 0X0A00, 0XCAC1, 0XCB81, 0X0B40, 0XC901, 0X09C0,
        0X0880, 0XC841, 0XD801, 0X18C0, 0X1980, 0XD941, 0X1B00, 0XDBC1, 0XDA81, 0X1A40,
        0X1E00, 0XDEC1, 0XDF81, 0X1F40, 0XDD01, 0X1DC0, 0X1C80, 0XDC41, 0X1400, 0XD4C1,
        0XD581, 0X1540, 0XD701, 0X17C0, 0X1680, 0XD641, 0XD201, 0X12C0, 0X1380, 0XD341,
        0X1100, 0XD1C1, 0XD081, 0X1040, 0XF001, 0X30C0, 0X3180, 0XF141, 0X3300, 0XF3C1,
        0XF281, 0X3240, 0X3600, 0XF6C1, 0XF781, 0X3740, 0XF501, 0X35C0, 0X3480, 0XF441,
        0X3C00, 0XFCC1, 0XFD81, 0X3D40, 0XFF01, 0X3FC0, 0X3E80, 0XFE41, 0XFA01, 0X3AC0,
        0X3B80, 0XFB41, 0X3900, 0XF9C1, 0XF881, 0X3840, 0X2800, 0XE8C1, 0XE981, 0X2940,
        0XEB01, 0X2BC0, 0X2A80, 0XEA41, 0XEE01, 0X2EC0, 0X2F80, 0XEF41, 0X2D00, 0XEDC1,
        0XEC81, 0X2C40, 0XE401, 0X24C0, 0X2580, 0XE541, 0X2700, 0XE7C1, 0XE681, 0X2640,
        0X2200, 0XE2C1, 0XE381, 0X2340, 0XE101, 0X21C0, 0X2080, 0XE041, 0XA001, 0X60C0,
        0X6180, 0XA141, 0X6300, 0XA3C1, 0XA281, 0X6240, 0X6600, 0XA6C1, 0XA781, 0X6740,
        0XA501, 0X65C0, 0X6480, 0XA441, 0X6C00, 0XACC1, 0XAD81, 0X6D40, 0XAF01, 0X6FC0,
        0X6E80, 0XAE41, 0XAA01, 0X6AC0, 0X6B80, 0XAB41, 0X6900, 0XA9C1, 0XA881, 0X6840,
        0X7800, 0XB8C1, 0XB981, 0X7940, 0XBB01, 0X7BC0, 0X7A80, 0XBA41, 0XBE01, 0X7EC0,
        0X7F80, 0XBF41, 0X7D00, 0XBDC1, 0XBC81, 0X7C40, 0XB401, 0X74C0, 0X7580, 0XB541,
        0X7700, 0XB7C1, 0XB681, 0X7640, 0X7200, 0XB2C1, 0XB381, 0X7340, 0XB101, 0X71C0,
        0X7080, 0XB041, 0X5000, 0X90C1, 0X9181, 0X5140, 0X9301, 0X53C0, 0X5280, 0X9241,
        0X9601, 0X56C0, 0X5780, 0X9741, 0X5500, 0X95C1, 0X9481, 0X5440, 0X9C01, 0X5CC0,
        0X5D80, 0X9D41, 0X5F00, 0X9FC1, 0X9E81, 0X5E40, 0X5A00, 0X9AC1, 0X9B81, 0X5B40,
        0X9901, 0X59C0, 0X5880, 0X9841, 0X8801, 0X48C0, 0X4980, 0X8941, 0X4B00, 0X8BC1,
        0X8A81, 0X4A40, 0X4E00, 0X8EC1, 0X8F81, 0X4F40, 0X8D01, 0X4DC0, 0X4C80, 0X8C41,
        0X4400, 0X84C1, 0X8581, 0X4540, 0X8701, 0X47C0, 0X4680, 0X8641, 0X8201, 0X42C0,
        0X4380, 0X8341, 0X4100, 0X81C1, 0X8081, 0X4040
        };
 
        //==========================================================================//
 
        //=========================================================================//
        //CRC16 을 BYTE[2] 로 리턴하는 함수
        //=========================================================================//
        public byte[] fn_makeCRC16_byte(byte[] bytes, int ilen)
        {
            int icrc = 0xFFFF;
            for(int i = 0; i < ilen; i++)
            {
                icrc = (icrc >> 8 ) ^ wCRCTable[(icrc ^ bytes[i]) & 0xff];
            }
            byte[] ret = BitConverter.GetBytes(icrc);
 
            return ret;
        }
    }