说明：  LRC校验函数说明及程序源码, 错误校验用于 ASCII 模式。这个错误校验码是一个 8 位二进制数，可作为 2 个 ASCII 十六进制字节传送。计算 LRC 码时，仅设备地址、功能代码、数据块字节参加
(LRC calibration function descriptions and program source code, check for errors in ASCII mode. This error check code is a binary number eight, as two ASCII hexadecimal byte transmission. LRC calculation code, the only equipment addresses the functional code bytes in the data block)