一段代码求详细解释

Question

下面 //// 内的代码没看懂,求详细解释!
            byte[] btMsg, btBuf;
            byte[] btSend;
            char[] chBuf;
            int iBt;
            DateTime dtNow = DateTime.Now;
            btMsg = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 };            //////////////////没看懂的内容///////////////////////
              btBuf = Encoding.ASCII.GetBytes(dtNow.Second.ToString("X2"));
            chBuf = Encoding.ASCII.GetChars(btBuf);
            iBt = Convert.ToInt16(chBuf[0]);
            iBt <<= 4;      // 为什么要这么做?
            iBt += Convert.ToInt16(chBuf[1]);
            btMsg[0] = (byte)iBt;  // 还有这个,大于255的数转成 byte 有什么作用?
            /////////////////////////////////////////

Answer 1

例如
                                                          
(int)60  --- 0x3C --- > btBuf 33 43 ---  chBuf '3' 'C' '3' ==33
'C' ==43;iBt ==  (0x33<<4)+0x43  0x373
取最后 0x73/... 
验效?

Answer 2

附方法全文:
public byte[] SetTime(Int16 desAddress)                           //设置时钟参数
        {
            byte[] btMsg, btBuf;
            byte[] btSend;
            char[] chBuf;
            int iBt;
            DateTime dtNow = DateTime.Now;
            btMsg = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 };            //计算秒
            btBuf = Encoding.ASCII.GetBytes(dtNow.Second.ToString("X2"));
            chBuf = Encoding.ASCII.GetChars(btBuf);
            iBt = Convert.ToInt16(chBuf[0]);
            iBt <<= 4;
            iBt += Convert.ToInt16(chBuf[1]);
            btMsg[0] = (byte)iBt;
            btBuf = Encoding.ASCII.GetBytes(dtNow.Minute.ToString("X2"));
            chBuf = Encoding.ASCII.GetChars(btBuf);
            iBt = Convert.ToInt16(chBuf[0]);
            iBt <<= 4;
            iBt += Convert.ToInt16(chBuf[1]);
            btMsg[1] = (byte)iBt;            btBuf = Encoding.ASCII.GetBytes(dtNow.Hour.ToString("X2"));
            chBuf = Encoding.ASCII.GetChars(btBuf);
            iBt = Convert.ToInt16(chBuf[0]);
            iBt <<= 4;
            iBt += Convert.ToInt16(chBuf[1]);
            btMsg[2] = (byte)iBt;
            btBuf = Encoding.ASCII.GetBytes(dtNow.Day.ToString("X2"));
            chBuf = Encoding.ASCII.GetChars(btBuf);
            iBt = Convert.ToInt16(chBuf[0]);
            iBt <<= 4;
            iBt += Convert.ToInt16(chBuf[1]);
            btMsg[3] = (byte)iBt;            btBuf = Encoding.ASCII.GetBytes(dtNow.Month.ToString("X2"));
            chBuf = Encoding.ASCII.GetChars(btBuf);
            iBt = Convert.ToInt16(chBuf[0]);
            iBt <<= 4;
            iBt += Convert.ToInt16(chBuf[1]);
            btMsg[4] = (byte)iBt;            iBt = (int)dtNow.DayOfWeek;
            btMsg[5] = (byte)iBt;            iBt = Convert.ToInt16(dtNow.Year.ToString().Substring(2));
            btMsg[6] = (byte)iBt;
            btSend = new byte[btMsg.Length + 9];
            btSend[0] = 0x7E;
            btSend[1] = 0x9B;
            btSend[2] = 0xFF;
            btSend[3] = 0xFF;
            btSend[4] = (byte)(desAddress >>= 8);
            btSend[5] = (byte)(desAddress & 0xFF);
            btSend[6] = 0x03;            btSend[7] = (byte)btMsg.Length;
            btMsg.CopyTo(btSend, 8);            btSend[btSend.Length - 1] = 0xAA;
            return (btSend);
        }