说明：  计算CRC校验和,可以计算modbus规约/CDT规约/DISA规约/DF1规约/DNP规约/1801等规约的校验和.
(and CRC calculation, modbus connection can be calculated Statute/CDT Statute/DISA Statute/DF1 Statute/DNP Statute/18 01 of the Statute, such as checksum.)